My idea for a DIY plywood aquarium

[coolkeith]

I will look into the underlayment..I am planning on just doing the corners and seams..I was thinking I would do 2 layers of a more flexible cloth and just alternate the "grain" of the cloth so it makes a sturdy seal. Do I need to let each layer of fiberglass dry before applying the new layer or do I wet the first layer and then put the second layer on after the first layer is completely wet?

You should always wet the substrates surface with epoxy before laying the fiberglass cloth on top of it. Otherwise, the epoxy probably won't completely soak through the cloth and adhere well to the substrate. You don't need to let each layer cure before adding another layer. Theoretically, you can keep adding layers of cloth to wet epoxy. It's like making a sandwich..... epoxy then cloth, epoxy, then cloth, then epoxy. With large sheets of cloth, that works well. But with thin strips of cloth, you need to be extra careful or you may disrupt/move the previous layer if it's still wet. So you may need to let the cloth set-up for several hours before adding another layer of fiberglass. You'll need to re-wet the surface though.


Some tidbits:

Avoid leaving mixed epoxy in large mass as it may overheat if left sitting. If mixing epoxy in large batches, after mixing, you'll need to pour the epoxy in a shallow container, so that some of the reactionary heat can escape. If the epoxy is left sitting in large mass, it can get hot enough to melt a plastic cup.
[video=youtube;3uzRaSJFWo4]https://www.youtube.com/watch?v=3uzRaSJFWo4#t=18[/video]

Mix batches of the colorant and resin at least a day before adding the curing agent, so that the resin will have time to de-gas.
You may want to buy a cheap pocket scale to accurately measure the colorant, resin, and curing agent. It's much easier to measure the products by weight instead of volume.
Get a box of disposable gloves. It can sometimes get really messy, so you might find yourself changing gloves every 10 minutes.
Need lots of disposable craft or stirring sticks.
You'll probably want a few different sizes of disposable paper or plastic cups.
If you use Max Bond Thixotropic, you may want to get a box of heavyweight plastic spoons for scooping it out of the containers.
If the Max ACR epoxy is too thin and drips to much for your liking, you can add Max Bond Thixotropic to it to thicken it up. If you do that, you should premix the resins together and premix the curing agents together, then let them de-gas overnight, since there will be a lot of air entrapment. I've used 50/50 ratio of each with excellent results. Gives one very thick coat (like Pond Armor) with little to no vertical dripping. 75% ACR / 25% BOND works well too.

Practice measuring/mixing the epoxy, and practice laying down the fiberglass cloth on some scrape pieces of wood.

Only mix as much epoxy as you can use as per instructions. Each brand of epoxy will be different. For example, for the Max ACR, you'll have about 60 minutes of work time with each batch. For Max Bond you'll have about 90 minutes of work time.

The epoxy gets harder to work with the longer it sits, so you'll want to use it as quickly as possible.

 

[Big Fish Freak]

You should always wet the substrates surface with epoxy before laying the fiberglass cloth on top of it. Otherwise, the epoxy probably won't completely soak through the cloth and adhere well to the substrate. You don't need to let each layer cure before adding another layer. Theoretically, you can keep adding layers of cloth to wet epoxy. It's like making a sandwich..... epoxy then cloth, epoxy, then cloth, then epoxy. With large sheets of cloth, that works well. But with thin strips of cloth, you need to be extra careful or you may disrupt/move the previous layer if it's still wet. So you may need to let the cloth set-up for several hours before adding another layer of fiberglass. You'll need to re-wet the surface though.


Some tidbits:

Avoid leaving mixed epoxy in large mass as it may overheat if left sitting. If mixing epoxy in large batches, after mixing, you'll need to pour the epoxy in a shallow container, so that some of the reactionary heat can escape. If the epoxy is left sitting in large mass, it can get hot enough to melt a plastic cup.


Mix batches of the colorant and resin at least a day before adding the curing agent, so that the resin will have time to de-gas.
You may want to buy a cheap pocket scale to accurately measure the colorant, resin, and curing agent. It's much easier to measure the products by weight instead of volume.
Get a box of disposable gloves. It can sometimes get really messy, so you might find yourself changing gloves every 10 minutes.
Need lots of disposable craft or stirring sticks.
You'll probably want a few different sizes of disposable paper or plastic cups.
If you use Max Bond Thixotropic, you may want to get a box of heavyweight plastic spoons for scooping it out of the containers.
If the Max ACR epoxy is too thin and drips to much for your liking, you can add Max Bond Thixotropic to it to thicken it up. If you do that, you should premix the resins together and premix the curing agents together, then let them de-gas overnight, since there will be a lot of air entrapment. I've used 50/50 ratio of each with excellent results. Gives one very thick coat (like Pond Armor) with little to no vertical dripping. 75% ACR / 25% BOND works well too.

Practice measuring/mixing the epoxy, and practice laying down the fiberglass cloth on some scrape pieces of wood.

Only mix as much epoxy as you can use as per instructions. Each brand of epoxy will be different. For example, for the Max ACR, you'll have about 60 minutes of work time with each batch. For Max Bond you'll have about 90 minutes of work time.

The epoxy gets harder to work with the longer it sits, so you'll want to use it as quickly as possible.

It seems to sound harder than it is. If I am understanding correctly, as long as the curing agent isn't added, the resin won't harden? When mixing the colorant and resin, would I leave them in an open container to degas or in a sealed container? I saw on their ebay page that one gallon of the epoxy will cover 1608 sq. ft. of area at a 1 mil thickness..it also says in their slideshow build of the plywood tank that 2 coats will seal it..so with my tank being ~100 sq. ft. I will be getting many coats out of 1 gal of epoxy. Unless my math is extremely off (which knowing me, it very well could be..) I was under the impression that I would need to get 2 gal to complete the project..

 

[coolkeith]

It seems to sound harder than it is. If I am understanding correctly, as long as the curing agent isn't added, the resin won't harden?

Yes, the epoxy resin won't harden, if the curing agent isn't added.

When mixing the colorant and resin, would I leave them in an open container to degas or in a sealed container?

The containers should be covered with some type of lid. I usually just put plastic wrap over the containers and any mixing tools that I want to reuse.

I saw on their ebay page that one gallon of the epoxy will cover 1608 sq. ft. of area at a 1 mil thickness..it also says in their slideshow build of the plywood tank that 2 coats will seal it..so with my tank being ~100 sq. ft. I will be getting many coats out of 1 gal of epoxy. Unless my math is extremely off (which knowing me, it very well could be..) I was under the impression that I would need to get 2 gal to complete the project..

Yes, your math is off.
1608 sq. ft. at 1 mil is the coverage for 1 gallon of any kind of liquid. There is 0.134 cubic feet in a gallon. There are 12,000 mils in a foot. (.134 x 12,000) = 1608 sq feet at 1 mil.

You need to use at least 2 coats of epoxy, but that depends on the thickness of each of the coats.

With exception of the initial wetting/impregnating layer, each coat of epoxy will be much thicker than 1 mil of thickness. For comparison, a single coat of normal paint is about 5 mils thick. For waterproofing an aquarium, I'd aim for about 30 mils in total thickness of epoxy (which is about 1/32"). So the math is that you'd get 53.6 sq. feet (1608 sq ft / 30 mils) of coverage at 30 mils thickness per gallon of epoxy. So that works out to 1.87 gallons to cover 100 sq feet at 30 mils of thickness. I'd add about 15% to that for over-spills/loss/ect. So to be safe, you'd need 2.15 gallons just to waterproof the inside of the tank. Max ACR comes in 1.5 gallon kits. Each coat of Max ACR, like paint, will be about 5 mils thick. So you'd need about 6 coats to get 30 mils of thickness. If you get Max Bond Thixotropic also, you can mix it to ACR to get thicker coats of around 10 mils each. So maybe get a 1 gallon kit of Max Bond also, so that you'll have 2.5 gallons total, for the inside of the tank. You'll probably only need a little more epoxy to waterproof the top and any bracing.

Another way to estimate how much epoxy you'll need, for greenterra's 800 gallon plywood build, where he used about 18 liters/4.75 gallons of epoxy (6 coats on the both the inside and outside). That tank measured 2700mm x 1200mm x 1032mm or 8.86 feet x 3.93 feet x 3.39 feet. About 92 sq feet for the inside the tank, which is about the same as yours. So you'll only need about half as much epoxy he used, if you don't plan to waterproof the outside with epoxy. I'd want to epoxy the outside, but regular exterior paint will do if you're on a budget.

 

[Big Fish Freak]

Yes, the epoxy resin won't harden, if the curing agent isn't added.

The containers should be covered with some type of lid. I usually just put plastic wrap over the containers and any mixing tools that I want to reuse.


Yes, your math is off.
1608 sq. ft. at 1 mil is the coverage for 1 gallon of any kind of liquid. There is 0.134 cubic feet in a gallon. There are 12,000 mils in a foot. (.134 x 12,000) = 1608 sq feet at 1 mil.

You need to use at least 2 coats of epoxy, but that depends on the thickness of each of the coats.

With exception of the initial wetting/impregnating layer, each coat of epoxy will be much thicker than 1 mil of thickness. For comparison, a single coat of normal paint is about 5 mils thick. For waterproofing an aquarium, I'd aim for about 30 mils in total thickness of epoxy (which is about 1/32"). So the math is that you'd get 53.6 sq. feet (1608 sq ft / 30 mils) of coverage at 30 mils thickness per gallon of epoxy. So that works out to 1.87 gallons to cover 100 sq feet at 30 mils of thickness. I'd add about 15% to that for over-spills/loss/ect. So to be safe, you'd need 2.15 gallons just to waterproof the inside of the tank. Max ACR comes in 1.5 gallon kits. Each coat of Max ACR, like paint, will be about 5 mils thick. So you'd need about 6 coats to get 30 mils of thickness. If you get Max Bond Thixotropic also, you can mix it to ACR to get thicker coats of around 10 mils each. So maybe get a 1 gallon kit of Max Bond also, so that you'll have 2.5 gallons total, for the inside of the tank. You'll probably only need a little more epoxy to waterproof the top and any bracing.

Another way to estimate how much epoxy you'll need, for greenterra's 800 gallon plywood build, where he used about 18 liters/4.75 gallons of epoxy (6 coats on the both the inside and outside). That tank measured 2700mm x 1200mm x 1032mm or 8.86 feet x 3.93 feet x 3.39 feet. About 92 sq feet for the inside the tank, which is about the same as yours. So you'll only need about half as much epoxy he used, if you don't plan to waterproof the outside with epoxy. I'd want to epoxy the outside, but regular exterior paint will do if you're on a budget.

So, I should go with about 3 gallons total to get the right thickness I will need? or if I get the 2 gallons and the Max Bond I should be able to do the whole tank? I'm also not doing the front where the window is gonna be so I am gonna need less overall..I would imagine about 20 sq. ft. less total..doesn't seem like much but if I go with 3 10mil coats that 60 square feet I don't have to cover..my initial judgement of 2 gallons should be good..

For the wetting/impregnating layer, is that the layer I want to put the fiberglass in? I would imagine so, but just want to be sure..

 

[coolkeith]

So, I should go with about 3 gallons total to get the right thickness I will need? or if I get the 2 gallons and the Max Bond I should be able to do the whole tank? I'm also not doing the front where the window is gonna be so I am gonna need less overall..I would imagine about 20 sq. ft. less total..doesn't seem like much but if I go with 3 10mil coats that 60 square feet I don't have to cover..my initial judgement of 2 gallons should be good..

For the wetting/impregnating layer, is that the layer I want to put the fiberglass in? I would imagine so, but just want to be sure..

I can't really understand why you wouldn't want to seal the front framing where the window is going. Unless you think the window and silicone will seal it. I don't know of anyone who tried that or who didn't waterproof the front framing. So you're kind of on your own there. It could work, as there are always more ways than one to do things, but it only takes a tiny pinhole leak in the silicone to ruin all your hard work.

There's are many methods for fiberglassing and most of them work fine. Even the worst ways have success in waterproofing wood, it's just much less quality. You have to do something majorly wrong for the epoxy or fiberglass cloth to delaminate on it's own. You should always apply the cloth to a wet surface. For the very first layer of epoxy, you can wet the plywood out, let it cure, then sand off any raised grain. Then start fiberglassing. This will help give you a mirror like finish. Or you can just skip that if you don't need a mirror like finish. Just wet the plywood, let the epoxy soak in for 10 minutes, then start fiberglassing. You can also pre-soak the fiberglass cloth pieces, then just squeegee off any excess, then apply the cloth wherever you want it. I've seen model rocket builders do it that way and I've tried it that way for some destructive tests. Probably hard to do for this large tank.

Probably the easiest way to do the corners is to get a 50 yard roll of fiberglass cloth that's about 4" wide. You can get rolls anywhere from 1" to 6" wide. I'd probably use 8 to 10 oz cloth. Use a rotary fabric cutter and square (instead of eyeballing with scissors) to get straight cuts, and so you don't fray the ends.

 

[Big Fish Freak]

I can't really understand why you wouldn't want to seal the front framing where the window is going. Unless you think the window and silicone will seal it. I don't know of anyone who tried that or who didn't waterproof the front framing. So you're kind of on your own there. It could work, as there are always more ways than one to do things, but it only takes a tiny pinhole leak in the silicone to ruin all your hard work.

There's are many methods for fiberglassing and most of them work fine. Even the worst ways have success in waterproofing wood, it's just much less quality. You have to do something majorly wrong for the epoxy or fiberglass cloth to delaminate on it's own. You should always apply the cloth to a wet surface. For the very first layer of epoxy, you can wet the plywood out, let it cure, then sand off any raised grain. Then start fiberglassing. This will help give you a mirror like finish. Or you can just skip that if you don't need a mirror like finish. Just wet the plywood, let the epoxy soak in for 10 minutes, then start fiberglassing. You can also pre-soak the fiberglass cloth pieces, then just squeegee off any excess, then apply the cloth wherever you want it. I've seen model rocket builders do it that way and I've tried it that way for some destructive tests. Probably hard to do for this large tank.

Probably the easiest way to do the corners is to get a 50 yard roll of fiberglass cloth that's about 4" wide. You can get rolls anywhere from 1" to 6" wide. I'd probably use 8 to 10 oz cloth. Use a rotary fabric cutter and square (instead of eyeballing with scissors) to get straight cuts, and so you don't fray the ends.

I am definitely gonna seal the front side where the window will be, but I'm not gonna put epoxy over the window right? And where the window is wood wont be..so I just figured I would be losing sq. ft. Where the window goes..
sounds like fiberglassing should be a breeze then..
So option one is epoxy, cure, sand, epoxy, rest 10, fiberglass, epoxy,cure..
Option two is epoxy, rest 10, fiberglass, epoxy, cure..
right?

 

[coolkeith]

I am definitely gonna seal the front side where the window will be, but I'm not gonna put epoxy over the window right? And where the window is wood wont be..so I just figured I would be losing sq. ft. Where the window goes..
sounds like fiberglassing should be a breeze then..
So option one is epoxy, cure, sand, epoxy, rest 10, fiberglass, epoxy,cure..
Option two is epoxy, rest 10, fiberglass, epoxy, cure..
right?

You don't put the window in until after you epoxy the inside of the tank. Then you adhere the window in place.

Yup those are 2 options. There are other methods also. Not using fiberglass. Doing fillets. Pouring the epoxy.

 

[Big Fish Freak]

You don't put the window in until after you epoxy the inside of the tank. Then you adhere the window in place.

Yup those are 2 options. There are other methods also. Not using fiberglass. Doing fillets. Pouring the epoxy.

Yes but you cut the hole for the glass before you seal it no? Speaking of the window, do I need to put silicone on the inside between the glass and wall? I have seen it done without putting it there, and only making a fillet between the glass and the exterior the glass touches. Are those both necessary places for silicone to go or is one enough?

I will do some looking into fiberglassing techniques on other builds and general fiberglass techniques..I will be using fiberglass because I plan on being able to move the tank if I need to..I think that not using fiberglass seals the fate of the tank that once moved, the epoxy can shift to the point of stress fractures and unless you go back and reseal, it is going to leak. Fiberglass IMO will give the rigidity needed to keep the corners and seams from flexing during a transport..
If I were to pour the epoxy, would I be doing less layers? I would realistically only be able to pour the bottom piece right? Can't pour on a vertical surface right?

 

[coolkeith]

Yes but you cut the hole for the glass before you seal it no? Speaking of the window, do I need to put silicone on the inside between the glass and wall? I have seen it done without putting it there, and only making a fillet between the glass and the exterior the glass touches. Are those both necessary places for silicone to go or is one enough?

I will do some looking into fiberglassing techniques on other builds and general fiberglass techniques..I will be using fiberglass because I plan on being able to move the tank if I need to..I think that not using fiberglass seals the fate of the tank that once moved, the epoxy can shift to the point of stress fractures and unless you go back and reseal, it is going to leak. Fiberglass IMO will give the rigidity needed to keep the corners and seams from flexing during a transport..
If I were to pour the epoxy, would I be doing less layers? I would realistically only be able to pour the bottom piece right? Can't pour on a vertical surface right?

You should cut the front frame before assembling the tank. Silicone the window to that frame after the tank is sealed. How much of an overlap you need is a good question. Some people might say you need about a 3" overlap. I haven't done a plywood build with such a large glass window, so I really don't know. I'll only use smaller windows that I can lift and silicone into place by myself, where I don't need much of an overlap. With a large window of around 8 foot long x 3 feet high, you're going to have some challenges. Even at 3/4" thick, that single glass sheet is going to weight about 234 lbs. Where 3/4" is a bit thin for tank this size and for such a powerful fish. So I have some doubts about just using plywood with no exterior framing. You really shouldn't cut corners with a tank this size.

Perhaps cut down the size of this tank to just an 8x4 footprint. Adding that extra 1 foot to the width is making this build way more difficult than it needs to be and is probably going to cost you a lot more money. Maybe build a bigger sump instead to get the water volume back. Maybe add some hydroponic filtration also. Where are you located at? If you got warm weather and plenty of sun light year round, take advantage of it.

And yes, fiberglass cloth or some kind reinforcement for the corners is a must. Yes, you can't pour vertically.

 

[Big Fish Freak]

You should cut the front frame before assembling the tank. Silicone the window to that frame after the tank is sealed. How much of an overlap you need is a good question. Some people might say you need about a 3" overlap. I haven't done a plywood build with such a large glass window, so I really don't know. I'll only use smaller windows that I can lift and silicone into place by myself, where I don't need much of an overlap. With a large window of around 8 foot long x 3 feet high, you're going to have some challenges. Even at 3/4" thick, that single glass sheet is going to weight about 234 lbs. Where 3/4" is a bit thin for tank this size and for such a powerful fish. So I have some doubts about just using plywood with no exterior framing. You really shouldn't cut corners with a tank this size.

Perhaps cut down the size of this tank to just an 8x4 footprint. Adding that extra 1 foot to the width is making this build way more difficult than it needs to be and is probably going to cost you a lot more money. Maybe build a bigger sump instead to get the water volume back. Maybe add some hydroponic filtration also. Where are you located at? If you got warm weather and plenty of sun light year round, take advantage of it.

And yes, fiberglass cloth or some kind reinforcement for the corners is a must. Yes, you can't pour vertically.

Yeah that was my plan with the window, I plan on having a 5" border on the front panel and I plan on bracing the inside of the front panel with a ripped 2x4 so that I have about 4" of overlap room for the window and support on all 4 sides of the window..
So let me see if I understand this right:
If I frame in the inside of the tank with 2x4s, that doesn't add any structural support
If I frame the outside of the tank with 2x4s, that will add structural support.

To me that sounds a bit backwards but that's why I'm not building houses I guess..

If you knew me personally, you would know that everything in my life is always about a challenge. I don't like to settle with the norm or what everyone else is doing..most of my graduating class is working at walmart or grocery stores and I went and opened a business..Most people keep small community tanks and I have been raising monster fish for the past 6 years. Most people want a pet lizard and I breed them. If I am not being challenged I get bored and lose interest. I am not going to be cutting corners on this tank, the only risk I am taking with this tank is the glass..I don't think that I am going to have an issue with the fish in this tank as the fish that is going into it is only going to be 15" max when it goes in and by the time I get the next tank built after this one it will probably only be 2.5' max..

I was considering changing to an 8x4 footprint..The next tank tho is going to have the same types of joints as the 8x5 footprint, so I wanted to get some experience in that aspect before I scale up..I may still do an 8x4 footprint just for the sake of cost..I will sketch up the materials needed and check the difference in cost and if it's close I will have some deciding to do..