Building a 1700 gallon Shark Tank by Joe Salvatori Making the decision to build the tank, was the easiest part of the whole process. I really had no idea what I was getting into, because there's not much information on building a tank of this scale out there. I was able to find some info on plywood tanks, such as the plans on GARF's (Geothermal Aquaculture Research Foundation) website. I found even less on building concrete tanks. My dilemma was this. Although I knew it would be the easier route to build a concrete tank, I didn't want anything that permanent. I knew I wouldn't tire of the tank, but what if I sold the house? What would it do to my resale value? I came to the realization that not everyone wants a 1700 gallon shark tank in their basement, and tearing out concrete would be a nightmare. I would have to make it removable, this meant building it from a material that would lend itself easily to disassembly. ( [FONT=Arial,Helvetica,Sans Serif]The first pieces. )[/FONT] The obvious choice was wood. The plans on garf were great, but simply would not be practical on a tank this long, and deep and BIG. With depth and length, comes pressure. Without some additional support and structural rigidity, a plywood tank would literally blow apart. The challenge with any aquarium whether it be glass, acrylic, wood or cement, is building the walls to withstand forces generated by the water pressure. The deeper the water, the higher the pressure per square inch. Dealing with this pressure means preventing warpage/bowing. In smaller tanks, this can be accomplished by increasing the thickness of the glass/acrylic, and adding support (cross bracing) to the top of the tank. Cross bracing alone, would not solve all of my problems I had to find other means to help prevent bowing and flex. I knew that the garf plans had worked for many, as long as they were sealed properly. I knew plywood walls coated in epoxy would work. The way I saw it, I had two obstacles to overcome. 1. Supporting the entire tank so it wouldn't unfold like a cardboard box when full. 2. Sealing the seams, and preventing them from splitting/leaking under pressure. ( [FONT=Arial,Helvetica,Sans Serif]This is how the tank supports and disperses the weight. )[/FONT] My basic plan, was to build a boat, but inside out. Support: I decided the best way to prevent bowing, would be to support the tank from the outside, using interlocking 4x4's as support bands. Basically, the tank would be encased in a wood skeleton, adding strength and support in all the high stress areas. So the tank would still be a plywood tank, with regular plywood walls, but reinforced from top to bottom, with the most reinforcement at the top. To do this, I would need to build the frame first, and in a sense, install the tank last. Sealing the seams: I felt the best way to seal the seams, was for there to be no seams at all. I wanted to make the interior of the tank one solid piece, and what better material for the job than fiberglass? I would seal all the corners with seam tape, and then lay several layers on the walls and bottom of the tank. On top of this, I would roll several layers of 2 part epoxy to add color and finish sealing the tank. ( [FONT=Arial,Helvetica,Sans Serif]The walls start to go up. I tried to build in as much support as possible.)[/FONT] Once I had the general idea of what I wanted to do, things really got tricky. I had to settle on a final tank design, choose and locate all building materials, design/fabricate filtration, figure out how I would heat/cool the tank, lighting, etc. etc. To make matters worse, was determining how to deal with approximately 14,000 lbs of water weight, and preventing the humidity caused by evaporation for destroying my house. I had witnessed tanks fail in the past, due to being unlevel, or being on pillars which allowed different points of the tank to move at different rates. At that point I decided my tank must not only be built on one solid slab of concrete, but also sit directly on the ground. My house was built over 12 years ago, so I knew the concrete had time to settle. I found that my concrete floor in the basement was over 6" thick, and the slab on which I intended to build the tank was level and free of cracks. At that point I concluded that my floor would support the weight, and was ready to begin construction. ( [FONT=Arial,Helvetica,Sans Serif]The first pieces of the top frame go in. )[/FONT] I started rough sketching the tank and once I had a decent design, I went at it. The dimensions are as follows: 104L x 66W x 57D, External 122L x 82W x 64H. As stated before, there would be no stand as I wanted the tank to float/settle with the slab on which it was built, plus I needed the headroom above. So construction began. I first laid the four outermost 4x4's. I cut down the side pieces from their 144" overall length, to roughly 128". I did this only to ensure that the tank would not overlap onto the next slab of concrete. The end pieces were cut at 86", and would fit in between the side pieces. The limiting factor on the width of the tank was not the concrete slabs, but rather the tank had to line up with a wall I would be build, and I figured I needed at least 36" behind the tank. The four boards were then bolted together using 1/2" x 9" lag screws. All holes were pre drilled 3/8" dia, to approximately 90% depth, and then countersunk 1.5" dia x .5 deep. The counterbores would allow for the 1.5" dia washers and the head of screw to be recessed into the wood. Note: All lag screws used on the tank were installed in this same manner. ( [FONT=Arial,Helvetica,Sans Serif]More of the top goes in. I sit and "ponder" as my wife calls it. She's beggining to think "pondering" is my new hobby. )[/FONT] Next I built what would become the support for the floor of the tank. I installed 6 cross beams. Two were installed at what would become the ends of the tank, spaced 3.5" from the frame. This would allow for the installation of corner posts. Next, I added 2 beams, spaced 1.75" off center, again allowing for a post. From there, I added two additional beams evenly spaced between the end and center beams. Following the installation of the cross beams, a series of shorter supports was added. These were installed lengthwise (perpendicular to) between the cross beams, and evenly spaced. I left all of these beams free floating in an attempt to allow for small amounts of flex. I felt that this system would best distribute/support the weight of the water. From there I installed the four corner post. These would extent from the concrete, to the absolute top of the tank. Therefore, their length was determined by allowing 36" of space for me to crawl on the tank during maintenance. Next I began installing the vertical posts which would support the walls of the tank. All posts were bolted in place using lags screws. Each of the four corners would eventually form a 90 degree angle made of up 3- 4x4 posts. This area would be where the walls of the tank met up, so I wanted as much support as possible. Several posts were installed along the end walls of the tank, and even more on what would be the back wall. ( [FONT=Arial,Helvetica,Sans Serif]My super helper wife lends a hand applying paint to all surfaces. )[/FONT] All post were tied together with additional 4x4's around the perimeter of the top of the tank. The post are held in place with 2 lag screws each on the top. One installed vertically and the other horizontally. All of the top brace 4x4's are tied together in an interlocking fashion as well. The top and bottom support bands would eventually be made up of 4- 4x4's on every side, all over lapping and interlocking. Lag screws were again used to bolt them all together along the length of the tank. They were installed in all four directions to tie the 4 boards together. In other words, if you were to look at a cross sectional view of these 4 boards, you would see the screws form a square pattern. ( Backside ) Six cross braces were added to the top of the tank using 4x4's. I felt this would serve two functions. First and most important was adding strength to prevent bowing. Second, they would give me something to crawl on during maintenance of the tank. I knew they would block some light, but I'm not keeping corals, and now that the tank is finished, you really cant tell. Next I built what would become the support for the window. I used 4x4's for this as well, and built a lip that would support the perimeter of the glass. I didn't want the glass sitting on the bottom of the tank, so I added another 4x4 to the bottom of the tank, which would raise the window 3.5". This design would support the glass on all sides by 3.5". At this point, the basic frame of the tank was complete. I then applied two layers of a product called Kilz to all surfaces of the wood. The purpose of this was not to protect the wood from the water which would be in the tank, but rather the water that may be in the air (humidity) and the occasional spill/splash. ( [FONT=Arial,Helvetica,Sans Serif]I start installing 2 layers of 3/4" plywood on all sides except the front. )[/FONT] Once the Kilz primer had time to dry, I installed the walls. The walls are made up of 2 layers of 3/4" plywood. The layers were installed one at a time, using 1.5" screws spaced 1" apart, down the length of each post. A standard sheet of plywood is not large enough to cover the entire area of the tank. So several pieces were used for each layer. When installing the second layer, I installed them in a "mirror image" fashion. This ensured that all seams on the first layer, were cover by a solid piece of wood on the second. In addition to the screws, liquid nails was used between all pieces of plywood, and in all seams. My goal was to make these walls as much of solid piece as possible. ( [FONT=Arial,Helvetica,Sans Serif]After all walls were in, my wife holds our first shark in the tank. A 9" black tip!! )[/FONT] Next came the most time consuming process of the project. Fiber glassing. I had made some small repairs to watercraft in the past, but this would be my first full scale fiberglass project. I called US Composites for some advice on what to use and how to use it. They set me up with a full roll of 36" wide 7 oz fiberglass cloth, a roll of 6" 10 oz fiberglass corner cloth, several gallons of resin and hardener, and all they necessary aluminum rollers and tools. I explained what I was doing to them, and they gave me lots of useful tips and information. They sent me a product called cabosil, which is used to thicken the fiberglass resin turning it into a paste of putty. This would be used as a filler for all of the corners, gaps, and screw holes. I also had them send me 25 graduated mixing containers in various sizes, as I knew my wife would flip if I ruined every piece of tupper ware she owned!!! ( [FONT=Arial,Helvetica,Sans Serif]This pic is deceiving. Its the only pic of the fiberglass stage. Truth is, this part of the project took me 3 weeks. VERY time consuming, I would never do this for a living. )[/FONT] A few days later, all of my materials arrived and I went at it. The first step was to fill all of the gaps, holes and seams. I mixed up approximately 16 ounces of resin, and added cabosil until it was the consistency of peanut butter. I didn't want to mix too much at one time, as the resin sets and begins to harden (approx. 15 min) fairly quickly. I used putty knives to fill in all imperfections, and then let it cure. 24 hours later, I would sand everything down, and do it again until it was perfect. If remember correctly, I had to do this 4 times. When I finished this process, I began laying the first layer of corner tape. I would brush/roll down a thing layer of resin first, and allow it to become tacky. Then I folded the 6" corner tape into a 90 degree angle (3" per side) and apply it to the corners of the tank. I used one piece all around the bottom of the tank. When I would come to another wall and had to turn, I would cut the bottom portion of the tape at a 45 degree angle, and fold it over. This allowed me to make the 90 degree turns without having to use another piece of fiberglass. I glassed all corners (vertical and horizontal) and allowed it to cure. I used the aluminum rollers to smooth the glass, and then applied another "light" layer of resin. It should be noted that the strength is not in the resin, it is in the fiberglass itself. You only want to use enough resin on the first layer to hold the glass in place, and wet the back side. Then after laying the glass, use only enough resin to wet the cloth thoroughly. After this first layer in the corners, I learned a valuable lesson. Fiber glassing is not nearly as easy I had once thought. Fiberglass cloth becomes quite slipper/slimy when wet with resin. Using the rollers to effectively smooth out all bubble and creases was an art. Too much pressure and the 15 minutes work is shot, as the glass will slip out of place. Too little, and you'll have bubbles/gaps between the walls and the fiberglass. ( [FONT=Arial,Helvetica,Sans Serif]Talk about arm pump!! This is just one pic of the sanding process, but the entire tank was sanded in between each coat (5) of fiberglass. This pic was taken during the final sanding. You can see the dust particles on the camera lens. )[/FONT] The next day, I sanded down all imperfections, and roughed up the resin. I used a DA sander with 120 grit to knock down any high spots, and then used sanding blocks with 220 by hand. The final coat was sanded with 400 and 600 grit by hand.This is an important step, and must not be overlooked. After laying each layer, and the resin has dried you must rough up the smooth/glossy finish so the next layer will adhere properly. I then shop vac'd all the dust up (I did this after every sanding) and began on the walls. The cloth was only 36" wide, so I would have to lay two overlapping layers to cover the surface of the walls. For the first layer, I cut pieces to the length of each wall before application. The process for the walls was identical to the corners, but tested my patience much more. First I'd roll a layer of resin, allow it to tack up, apply the cloth, roll out the bubbles/creases, and then roll on another layer of resin. The learning curve for the walls was not much fun. One wrong move, and 30 minutes work is ruined. The best advice I can give for glassing the walls is #1 have a helper, and #2 be patient. I finished all of the walls, and then did the floor working my way out of the tank. 24 hours later I sanded everything down, and started the whole process over again. Corners, cure, sand, walls, cure, sand. I repeated this process three times, and then changed my methods. For the final two layers, I did not use corner tape. Instead, I laid 1 piece sheets along all three walls, and then down the walls and across the floor. I hoped this would give a smoother appearance when finished by hiding the small ridges left at the seams. ( [FONT=Arial,Helvetica,Sans Serif]This was the first coat of 2 part epoxy. I applied a total of three coats, each a different color, to ensure 100% coverage )[/FONT] he front wall of the tank, where the window would mount was also treated to five layers of fiberglass during the process. I used the 6" tape on this surface, and paid special attention to bubbles/creases when glassing. Since this would be the mounting surface for the glass, it needed to be extra smooth and flat. I sanded out any imperfections, and even spread a thin layer of thickened resin (using cabosil) on the surface to fill any tiny holes/gaps. I spent alot of time making sure this surface was as close to perfect as possible. The whole fiber glassing process took me roughly 2 months. Much longer than I had anticipated. I'm sure a professional could have done it MUCH faster, but I really took my time and did it the best I could. Fiberglass itself is not 100% waterproof in long term immersion, and I certainly didn't like the color of the tank. So next I contacted Aquatic Ecosystems. In my opinion, anyone serious about DIY aquaria needs to know about Aquatic Ecosystems. Their staff is very knowledgeable, and they carry just about anything you may need. They sold me a product called Sweetwater Epoxy Paint. This is a 2 part epoxy which is EPA approved and non toxic, even for drinking water. They assured me that this is a very tough paint, and would easily withstand the tests of long term immersion in a marine application. I applied a total of 3 coats of epoxy, each a different color starting with white. Its very important to follow the instructions for this epoxy. Its also worth noting that this stuff is very toxic, its even considered HAZMAT. The room must be well ventilated, and you must wear a mask while in the room. Over the course of 2 days, I rolled/brushed on the three coats. One coat was also applied to all external surfaces of the tank. I gave the epoxy about 2 weeks to cure before working on the tank anymore. ( [FONT=Arial,Helvetica,Sans Serif]The 3rd and final coat of 2 part epoxy. The pic is not of very high quality. The color is actually a fairly bright blue. Not near as dark as it seems. ) [/FONT] ( 3rd coat , [FONT=Arial,Helvetica,Sans Serif]Another view. )[/FONT] ( Inside View after glass install , [FONT=Arial,Helvetica,Sans Serif]I took this pic to show how I supported the window during the curing process) [/FONT] Next came the installation of the window. I chose acrylic over glass for my window, based on weight, cost, clarity, and personal preference. I've owned several acrylic tanks, and I've never had any trouble with them scratching if I was careful. After doing alot of research (and a bit of math) I decided to go with 1.5" cast acrylic. 1.5" is probably a little thick than necessary (so is the rest of the tank) but I was able to buy it for a good price, and felt more comfortable with the added strength given by the extra thickness (again same story with the rest of the tank, over built). ( [FONT=Arial,Helvetica,Sans Serif]Peeling off the masking. This was lots of fun. ) ( [/FONT][FONT=Arial,Helvetica,Sans Serif]Silcone work done. Time for a beer, and to pray I did it all right. )[/FONT] [FONT=Arial,Helvetica,Sans Serif] [/FONT] The window would be installed using silicone as a gasket. The silicone itself would not hold the window in place, or add any strength to the tank, as silicone does not really bond to acrylic. I would rely on water pressure alone to hold the window in place. Choosing a silicone was no easy task either. I really couldn't find much information on what silicone professional aquarium builders use on a tank of this scale. I contacted GE, DAP, and a few others regarding my situation. I found no help there. In fact, when I explained what I planned to them, they all stated (with the exception of DAP) that their product was not intended for use in aquariums. I found a brand sold by Aquatic Ecosystems, called Star Brite Marine Silicone. They state that this brand is intended for, and safe to use on aquariums, so I decided to use it. I purchased 15 tubes of the silicone from Aquatic Eco. Before installing the window, I made some "braces" (six) from pvc tubing and fittings. The purpose of these braces would be to span from the window, to the back of the tank and hold the window in place while the silicone cured, and until the tank was full of water. The braces had a threaded union on one end that would allow approx. 1" of adjustment. ( [FONT=Arial,Helvetica,Sans Serif]This was the first day of filling the tank. I wanted to fill it in small increments, so in the event of a leak, I'd know before I had to drain tons of water )[/FONT] When it was finally time to install the window, I lined the tank with used carpet to prevent any scratches during installation. Six friends helped me lift the window through the front of the tank. After a test fit, we moved the window to the back of the tank, and began applying the silicone to the 3.5" seating surface. Because silicone begins to set rather quickly, I had three caulking guns on hand, so three of us could apply 15 tubes in a timely manner. We applied 1/2" beads all around the surface until it was 100% covered. I realized this would make a mess once the window was set into place, but I figured it was easier to clean excess silicone, than it would be to remove the window and start over if it leaked. ( [FONT=Arial,Helvetica,Sans Serif]The 2nd day of filling. It holds water!! ) [/FONT]( [FONT=Arial,Helvetica,Sans Serif]Almost full! )[/FONT] Next we lifted the window into place, and applied uniform pressure until the space between the window and mating surface was approx. 1/4". We quickly put the braces into place while others were removing excess silicone on the outside of the tank. For added protection, I used another 5 tubes to seal around all of the edges of the window inside the tank. After snugging up all of the braces, it was time to wait. ( [FONT=Arial,Helvetica,Sans Serif]Swimming... I had to do it. )[/FONT] I let the tank sit for two full weeks before adding water. I didn't want to take the chance of the silicone still being wet since it was so thick in some places. When I finally did begin adding water, it was both a very exciting and nerve wracking experience. I added the water VERY slowly over the course of several days, in 100-200 gallon increments. This allowed me to really keep an eye out for leaks, and I felt better letting the tank/foundation slowly adjust to the weight/pressure. Its worth noting that I left each of the braces in place until the water line reached them. ( [FONT=Arial,Helvetica,Sans Serif]Heres the mazzai 1" venturi, a 1.5" check valve, a 1.5" bulkhead, and a massive 4" bulkhead. The measure 9.5" on the O.D.!! Our cat gives a good comparison. ) ( Plumbing Supplies ) [/FONT] eeing the tank full, without any leaks was an unforgettable feeling of accomplishment. So much so in fact, that I couldn't help taking a swim "just to check on things." To boost my confidence level in the tank, I let it sit full of water for over a month. During this time I started piecing together my circulation/filtration and plumbing. For a sump, I considering using a large used aquarium. Finding one at a decent price, or in decent condition became a problem, so I looked into alternatives. I had heard of people using plastic (Rubbermaid) containers as sumps, so I figured I could do the same on a larger scale. I contacted a local ranch supply store to see what they had. I ended up with a large (8x3x2.5) plastic horse trough. The trough even had a built in threaded drain at one end near the bottom, which would work perfect as a bulkhead. I brought it home, made some baffles out of 1/4" acrylic (4), and installed them using silicone. The baffles were position just like any other sump. The water would have to flow under 2 and over 2. I used 2 5 gallon buckets as chambers for the incoming water. I drilled hundreds of 3/8" holes in the bottom, and cut 1/2" wide slots on a 180 degree portion of the side of the buckets. Bio balls, and chemical filtration would be placed in the buckets, water would flow in the top, over the media, out the holes/slots, and into the first chamber of the sump. I then drilled four 3/4" holes in the buckets approx. 5" from the top. The holes were positioned in a matter that would allow me to insert two 36"x3/4" dia plastic rods through the holes, parallel to each other and spaced 10" apart. These rods would support the buckets on the top of the sump, over the first chamber. The buckets were installed on the opposite end of the drain hole (bulkhead) and I used 1/2 round clamps to secure them in place. ( [FONT=Arial,Helvetica,Sans Serif]The skimmer is 6' tall and is a venturi. ) [/FONT] or a protein skimmer, I had decided that I would either build my own, or buy one. I was ready to do either, when I stumbled upon a used 6' skimmer at my lfs. It was one they had used to skim all of their tanks, but was taken out of service due to a broken collection cup. They had also removed the venturi from the skimmer. I jumped at their offer to sell the skimmer for $50, made a new collection cup from pvc, and installed a mazzai venturi. For added filtration I purchased 2 40w UV steralizers, and 2 fluidized bed filters (rated at 900 gallons each) from rainbow lifegard. I called aquatic ecosystems and purchased 3 8'x3' rolls of mechanical filtration media, varying in thickness and porosity. I cut these to the size and shape I needed, and installed them in the sump between the baffles. Now came the time to drain the tank, and cut holes for the bulkheads which would act as exits/returns for my filtration. ( [FONT=Arial,Helvetica,Sans Serif]Sump install. ) [/FONT]( All the plumbing done except the overflow pips. ) I drained the tank slowly, and reinstalled the cross braces to support the window as it drained. Once empty I measured and marked where I would install the bulkheads. I again called Aquatic Ecosystems, and purchased a total of 6- 1 1/2" bulkheads, and 2 4" bulkheads. The two 4" bulkheads were installed on the right hand end of the tank, near the top. These would act as my overflow points for the sump. I purchased two 90 degree street elbows from Home Depot, and inserted them into the 4" bulkheads. The elbows are turned approx. 30 degrees, and the bulkheads were installed lower in the tank to adjust for my water height when full. Two of the 1.5" bulkheads were installed 6" below water line, and would serve as returns from the open loop (sump). They were installed on opposite ends of the tank, one left hand and the other right. I placed the bulkheads on every wall, at various heights to get as much circulation as possible and prevent dead spots. Three of the remaining 1.5" bulkheads were installed 30" below water line. Two on the back wall, and one on the right hand side. The last bulkhead was installed 20" below water line on the back wall. These 4 bulkheads would be on a closed loop. I used one of the bulkheads (30" below water line) as an inlet for the closed loop. The other two at 30" were used for circulation only at max flow rate (no filters on them). The last bulkhead would return filtered water from my fluidized bed filters and UV steralizers. ( [FONT=Arial,Helvetica,Sans Serif]Side plumbing. )[/FONT] I purchased 2- 3/4 hp 5000gph pumps from Rainbow Lifegaurd. One would run the open loop, and the other would run the closed loop. I first installed ball valves on all of he 1 1/2" bulkheads. I also installed check valves with unions on the two bulkheads which would return water from the sump (open loop) to prevent an over flow in the event of a power outage. I plumbed the inlet from one pump to the drain/bulkhead on the sump. I then built a manifold with two outlets and ball valves for the outlet of the open loop pump. Using 1 1/2" flexible PVC tubing I ran lines to the two upper bulkheads with the check valves on them. Next I installed the drains from the two 4" bulkheads/overflows. I used 4" pvc tubing, and ran one line to each of the 5 gallon buckets on the sump. Once the open loop was complete, I plumbed one of the lower bulkheads (30") to the inlet of the other pump, with an additional ball valve near the inlet. This pump would run the closed loop. I built another manifold with 4 outlets and ball valves on each one. Two of the outlets were plumbed to the remaining two bulkheads at 30" below water line. One was plumbed to the fluidized bed filters, then through the UV's, and then to the last bulkhead (20" below water line). I used the 1 1/2" flexible PVC tubing on all of the lines. The remaining outlet on the manifold was to be used as a back up, but I later installed a canister filter onto it, which returns water to the top of the tank through a spray bar. To power the protein skimmer, I used a 1200 gph submersible pump. This pump draws water from the sump, through the skimmer, and returns it to the sump. ( [FONT=Arial,Helvetica,Sans Serif]I added 200lbs of sand, it barely made a difference. Adding another 700lbs soon. )[/FONT] ( Lots of salt. ) (Salt in ) ( [FONT=Arial,Helvetica,Sans Serif]4 days after I refilled the tank and started the pumps, two of the five 1.5" bulkheads started leaking. Was not fun to fix)[/FONT] I gave the glue on all of the plumbing 24 hours to dry, and refilled the tank. I turned on the closed loop pump first, and used this as a means to mix in the salt. Next began the very time consuming task of rinsing and adding 800lbs of sand. I used a mixture of Carib Sea Aragonite, Aragomax, and Southdown Play Sand. Then I continued filling until water began to over flow into the sump. When the sump was nearly full, I powered up the open loop pump and adjusted the salinity. ( [FONT=Arial,Helvetica,Sans Serif]The overflows are 4" dia. ) [/FONT] I let everything run for a week or two to see if I'd have any problems. To be honest, I did. 3 of the 1 1/2" bulkheads began to leak, and I had alot of bubbles being returned to the tank from both pumps. I traced the leaking bulkheads back to my installation procedure. I had read many opinions on the best way to install bulkheads. One common suggestion was to apply silicone sealant to the rubber gaskets during installation. So I did. This proved to be a fatal error on my part. In my opinion adding silicone sealant to the gaskets will almost guarantee that they DO leak, not help prevent it. My opinion is based on the following: 1. The silicone will make the gaskets slippery during installation. This will cause the gaskets to tend to slip out of place when being compressed between the two surfaces. 2. If the bulkheads are moved/retightened after the silicone has had a chance to set, then the silicone will "ball up" creating voids between the bulkhead and wall. These voids will eventually leak. So I drained the tank below the bulkheads, and replaced all of the gaskets. This process was made much worse by the fact that I had to try to save/store over 1000 gallons of saltwater. Lesson Learned. (Over Flow) ( Overflow Exits ) The bubbles being returned to the tank turned out to be a combination of problems. The open loop pump had a small leak at the inlet, which allowed air to be sucked in when the pump was powered up. I did not find this problem until I shut the pumps down for about an hour to look for leaks. The bubble problem on the closed loop pump turned out to be cavitation. To cure the problem, I simply cut back the flow (about 5 degrees) using the ball valves on the manifold. After another 3 week test period, I began adding my live rock, live sand, and a few damsels to get my cycle kicked off. During the cycle period, I constructed a 12" wide splash guard from 1/4" acrylic which surrounds the perimeter of the tank. The prevents the waves and occasion splash from a shark from making a mess on the side of the tank. It also helps with evaporation. I also added a heavy duty 3/16" thick plastic net to the top of the tank which is held in place with a series of hooks and cords. The purpose of the net is to prevent the sharks from jumping out of the tank. ( [FONT=Arial,Helvetica,Sans Serif]I have the LR in. 150lbs. And the LS 200lbs on top of 800lbs aragonite. I plan to add more LR in the near future. ) [/FONT] ( [FONT=Arial,Helvetica,Sans Serif]Here's a picture of my wife and our baby. The shark shown here is a leopard shark. He's only about a foot long right now, but will grow much larger ) ( [/FONT][FONT=Arial,Helvetica,Sans Serif]This picture shows a view above the tank, inside the tank room.)[/FONT] [FONT=Arial,Helvetica,Sans Serif] [/FONT] For lighting, I simply purchased 4 48" double bulb fluorescent lighting fixtures, with cold start ballast's from Home Depot. I purchased 8 48" aquarium bulbs, 4 actinic and 4 daylight. The lights are suspended over the tank on chains, and on a timer for 6 hours. ( [FONT=Arial,Helvetica,Sans Serif]This was the first shark added to the tank. She is a Horn Shark. She's a benthic "bottom dwelling" shark, and spends most of her time laying around. These sharks are nocturnal feeders, so she is most active at night. ) [/FONT]( [FONT=Arial,Helvetica,Sans Serif]These are my two benthic sharks. They are pretty good friends. ) [/FONT] I took several measures to control the excess humidity generated by the tank. Green board was used on all non-concrete walls in the tank room. I sealed all of the concrete walls with several coats of concrete sealant. Next I lined the entire room with heavy gauge plastic lining. I added air exchange fans to keep a constant supply of fresh air in the tank room. A large exhaust fan is in the works, which will draw air from above the tank, and vent to the exterior of the house, and I have a large dehumidifier on order. The rest is history. As of today 03/29/2003, the tank itself has held water without any leaks, signs of stress or warpage for 9 months. The entire system has been trouble free since the initial bulkhead incident 6 months ago. ( [FONT=Arial,Helvetica,Sans Serif]This shark is the reason I built the tank. He's about 22" long, and very active. He's a open water shark, and he never stops swimming. Not even when he sleeps. ) ( [/FONT][FONT=Arial,Helvetica,Sans Serif]In this pic, you can see the black tip swimming right by my head.)[/FONT] [FONT=Arial,Helvetica,Sans Serif] (Drywall) ([/FONT][FONT=Arial,Helvetica,Sans Serif]All the framing, electrical, and drywalling is complete, awaiting texturing and painting. )[/FONT] [FONT=Arial,Helvetica,Sans Serif] ( [/FONT][FONT=Arial,Helvetica,Sans Serif]My basement no longer feels like a cold, dark, useless space!! Its becoming the "Den" I had envisioned all along. Just need to finish the floors now.) [/FONT][FONT=Arial,Helvetica,Sans Serif] [/FONT] The purpose of this article is to give an overview of what I did, and how I did it. I would like to point out that what has worked for me may not work for you. I in no way make any guarantees or promises on the design/plans listed above. In other words, build this tank at your own risk If there is any additional information anyone would like, please feel free to either post your questions/comments here, or contact me directly at firstname.lastname@example.org.