Half way into an all-steel Aquarium

[Ianf406]

Good evening!

I work at a Steel and yard and wanted to build my own aquarium. So I have been! I read a ton abiut plywood aquariums but hate working with wood.

Its 96.5" wide, 36.5" tall and 26" deep. (About 400 gallons) it's going in my garage and I couldn't make it that much larger. Everything (including the glass) weighs 1266LBs. Total cost so far ~1500$. Stand was cut on a tube laser. Tank itself was made in two pieces on the plasma table/break. Cut the holes in the acrylic on a water jet. I drew it all up and did all the welding.

Im about a month in. I've got it mostly constructed and just put the first coat of pond liner over a few layers of fiberglass and total boat marine resin. I hit the inside with a rough grinder, then a stripping wheel, then 40 grit sandpaper prior to cleaning it with alcohol. Still have the sump to do.

My question is reguarding the acrylic sheet.
I have a 96x36x.75" sheet of cast acrylic.
Plan is to bolt it together. 3/16 steel----> fiberglass/pond liner---> Silicone---> acrylic----> red hdpe "gasket" shown in one of the pictures.

I have SS nuts/bolts with nylon washers. Plan on filling the holes in the acrylic before bolting it all together.

1. Anyone know what I can torque a bolt against acrylic too? Chat GPT says 30 ft/lbs... seems a little excessive.

2. The flange around all outside edges of the acrylic is 4.5" and made of 3/16 A36 steel. I plan on using a TON of silicone. Is there a product that works better with acrylic? I plan on aquascaping the back wall (all rock/roots) then lifting the acrylic up, down and into position so work time for whatever sealant I use has to give me a little time to line up bolt holes and the like.

Thanks!

 

[jjohnwm]

As one fan of overkill speaking to another...I salute you, sir!

 

[kjfan1]

It looks amazing, keep up the good work!

 

[danotaylor]

Looks like a serious build!! Never seen a steel aquarium b4

Unfortunately I don’t have the answer to your 2 queries.

I do have a question though about the choice of acrylic thickness. I am not an engineer, so just punter throwing this out there.

I have a 120”x36”x30” acrylic tank. The vertical height is 30” and the manufacturer used 1” thick acrylic. I realize the build is different in many ways, but a constant is how pressure water exerts on the structure at 36” tall. This will be a massive amount of water pressure. After installing the viewing panel will you install cross bracing to minimize flexing?

Watching with great interest

 

[duanes]

Back when I was a snot nosed kid. all tanks were metalframe.

 

[Ianf406]

Looks like a serious build!! Never seen a steel aquarium b4

Unfortunately I don’t have the answer to your 2 queries.

I do have a question though about the choice of acrylic thickness. I am not an engineer, so just punter throwing this out there.

I have a 120”x36”x30” acrylic tank. The vertical height is 30” and the manufacturer used 1” thick acrylic. I realize the build is different in many ways, but a constant is how pressure water exerts on the structure at 36” tall. This will be a massive amount of water pressure. After installing the viewing panel will you install cross bracing to minimize flexing?

Watching with great interest

I'm hoping that the 1/4" SS bolt every 6" combined with the steel flange and HDPE "Washer" on the inside of the glass should stop the arcylic from bowing at all. From my research it appears it only bows when the edges pull away giving the center room to bow. That shouldn't happen bolted through steel (I hope). I have not seen any proof of any acrylic ripping or tearing.

As far as the steel across the front on the top it was all bent on a 500 ton press break (3/16 thick) I will have some bracing on top and when I get home I'll snap a picture to show ya what that will look like!

 

[wednesday13]

Fellow steel frame tank builder here… top notch work … super clean across the board and waaaaaaaaaaay more than u needed across the board also. No need to even fiberglass metal, just needed an epoxy paint coating.

As for the HDPE “gasket”… dont use it. For real tho, dont use it. Its a petroleum based product and nothing, absolutely nothing will stick to it even as a “real” gasket. If it were 1/4”-1/2” solid butyl rubber it would be an actual gasket and you would not need silicone at all. Especially with ur extreme overkill of bolt holes. I have a 3/4” window, steel frame and actual epdm pond liner u bolted at 8’x30” window. Zero bolts. In ur case and all cases with silicone being used there is zero torq required. U do not want to push out all the silicone u put in by cranking on the bolts. They should be hand tight and i would even recommend a spacer inbetween to prevent you from squeezing out too much silicone compromising ur gasket seal.

If u have access to a laser cutter and u already drilled/lasered a bunch of holes in ur acrylic i would try making a “real” gasket in rubber and bolting it with no silicone at all. That method has been proven and there u would need pressure to seal it like a bulkhead.

If you go the silicone route. There are better silicones out there to answer ones of your questions. I used “hutton products” gold label aquarium pond sealer (silicone) with 15 yrs seal so far un bolted and thats to epdm pond liner thats a weaker bond than acrylic to epoxy. I also put up an acrylic window with 3m 5200 to pond liner bolted. Not as good in my opinion as the gold label but it worked fine. A more recent and proven multi materials silicone is “my pond” brand ms300… sand ur acrylic window also where its touching the silicone for the best adhesion possible. Sand with 220 grit then wipe clean with a mild rubbing alcohol or nail polish remover WITHOUT acetone…

I recommend 12 tubes of silicone, thats what i put on basically the same size window. Everyone skimps here. Ideally the window is sealed 3 times. Once inbetween, once on the outside and once on the inside. Things are different for glass but acrylic has very poor adhesion with silicones, even the “specality” ones.

Keep re reading ur posts lol… u say the HDPE is a gasket 1 time and a washer another lol… even as a washer i feel u might be shooting urself in the foot. When bolted u have to cover the bolt head also for another seal. I had a tank leak from that before. Probably be fine with loads of silicone as a real gasket but thats also a direct hole to the front/outside and again, silicone does not adhere to HDPE or HDPP… my steel frame tank is actually lined with HDPP and its heat welded at the seams for that reason.

Ur window is way more than fine as well with 3/4”. 2” surround seal is plenty and u did 4”. Acrylic bows because of height not surround support. Say if u used half inch it would bow alot more but ur bolts would hold it in place.

Lastly… would you ask chappy PTG for welding advice ? I hate robots and they give false info. Again, killer build so far … it will survive the apocalypse lol… 1”x1/8” box tube is all ya needed for that stand …

 

[Ianf406]

Fellow steel frame tank builder here… top notch work … super clean across the board and waaaaaaaaaaay more than u needed across the board also. No need to even fiberglass metal, just needed an epoxy paint coating.

As for the HDPE “gasket”… dont use it. For real tho, dont use it. Its a petroleum based product and nothing, absolutely nothing will stick to it even as a “real” gasket. If it were 1/4”-1/2” solid butyl rubber it would be an actual gasket and you would not need silicone at all. Especially with ur extreme overkill of bolt holes. I have a 3/4” window, steel frame and actual epdm pond liner u bolted at 8’x30” window. Zero bolts. In ur case and all cases with silicone being used there is zero torq required. U do not want to push out all the silicone u put in by cranking on the bolts. They should be hand tight and i would even recommend a spacer inbetween to prevent you from squeezing out too much silicone compromising ur gasket seal.

If u have access to a laser cutter and u already drilled/lasered a bunch of holes in ur acrylic i would try making a “real” gasket in rubber and bolting it with no silicone at all. That method has been proven and there u would need pressure to seal it like a bulkhead.

If you go the silicone route. There are better silicones out there to answer ones of your questions. I used “hutton products” gold label aquarium pond sealer (silicone) with 15 yrs seal so far un bolted and thats to epdm pond liner thats a weaker bond than acrylic to epoxy. I also put up an acrylic window with 3m 5200 to pond liner bolted. Not as good in my opinion as the gold label but it worked fine. A more recent and proven multi materials silicone is “my pond” brand ms300… sand ur acrylic window also where its touching the silicone for the best adhesion possible. Sand with 220 grit then wipe clean with a mild rubbing alcohol or nail polish remover WITHOUT acetone…

I recommend 12 tubes of silicone, thats what i put on basically the same size window. Everyone skimps here. Ideally the window is sealed 3 times. Once inbetween, once on the outside and once on the inside. Things are different for glass but acrylic has very poor adhesion with silicones, even the “specality” ones.

Keep re reading ur posts lol… u say the HDPE is a gasket 1 time and a washer another lol… even as a washer i feel u might be shooting urself in the foot. When bolted u have to cover the bolt head also for another seal. I had a tank leak from that before. Probably be fine with loads of silicone as a real gasket but thats also a direct hole to the front/outside and again, silicone does not adhere to HDPE or HDPP… my steel frame tank is actually lined with HDPP and its heat welded at the seams for that reason.

Ur window is way more than fine as well with 3/4”. 2” surround seal is plenty and u did 4”. Acrylic bows because of height not surround support. Say if u used half inch it would bow alot more but ur bolts would hold it in place.

Lastly… would you ask chappy PTG for welding advice ? I hate robots and they give false info. Again, killer build so far … it will survive the apocalypse lol… 1”x1/8” box tube is all ya needed for that stand …

You are correct! I called that HDPE several different things haha. It is not a gasket in any way- sort of a washer.

The HDPE is on the inside of the tank (steel--->acrylic---->HDPE) and not really part of the seal. No silicone involved with it. It along with my plumbing are red and mostly for looks.
2nd function was just mostly that I wanted to spread out the load from the bolts (not tightening washers/nuts directly against the acrylic).

I thought about cutting a rubber gasket- i just have not been able to source a big chunk of proper rubber locally. Perhaps that is the best way to tackle this. I could probably even just throw that HDPE over it as a template and cut it with a knife.

I was considering using automotive Blue RTV/gasket maker for the Seal and then silicone around the interior to avoid it leaching into the water.

Spacers are not a bad idea at all! What would you use? Nylon or something?

I used 4x4 .120 as I didn't want skinny little legs. Plan on running lights through the stand and that is why the holes are in there.
PLUS it is on my wifes side of the garage so......

Fiberglass was just because it is in the garage and will experience quite a few temperature fluctuations. Garage is heated and the fish I plan on keeping wont care but I know the steel will expand/contract differently than the epoxy and did not want that epoxy to crack apart.

 

[wednesday13]

You are correct! I called that HDPE several different things haha. It is not a gasket in any way- sort of a washer.

The HDPE is on the inside of the tank (steel--->acrylic---->HDPE) and not really part of the seal. No silicone involved with it. It along with my plumbing are red and mostly for looks.
2nd function was just mostly that I wanted to spread out the load from the bolts (not tightening washers/nuts directly against the acrylic).

I thought about cutting a rubber gasket- i just have not been able to source a big chunk of proper rubber locally. Perhaps that is the best way to tackle this. I could probably even just throw that HDPE over it as a template and cut it with a knife.

I was considering using automotive Blue RTV/gasket maker for the Seal and then silicone around the interior to avoid it leaching into the water.

Spacers are not a bad idea at all! What would you use? Nylon or something?

I used 4x4 .120 as I didn't want skinny little legs. Plan on running lights through the stand and that is why the holes are in there.
PLUS it is on my wifes side of the garage so......

Fiberglass was just because it is in the garage and will experience quite a few temperature fluctuations. Garage is heated and the fish I plan on keeping wont care but I know the steel will expand/contract differently than the epoxy and did not want that epoxy to crack apart.

I kinda gathered towards the end of ur post the red HDPE was a washer to sandwich the acrylic in. Very smart there i agree to dispurse the bolt pressure. The end of the bolt and that space between both sides of the poly is worrisome tho for water getting through. Even if u silicone the inside holes id use 2 rubber washers. One on each side of the hdpe. That should seal ya up and actually seal against the poly.

Back to the window debate… i wouldn’t use 2 different materials. Silicone alone can be a great gasket. The hutton products gold label is excellent stuff. Its expensive but worth it. I paid $430 for 12 tubes back in 09’ … I think the my pond brand ms300 is around the same price but again proven many times over. Both products are hard to get in the US is the other kicker. I had to order through a local pond shop and they had no idea what it was. Got lucky and it was in their sales catalog. Y i used 3m5200 for a build after. Its cheaper and available in the US. Black 3m5200 will cost u more but will look good with ur red/blackish tank. Theres also CT1 construction adhesive (black only is fish safe) thats been proven for “mixed materials” and available easier in the US. All pretty pricey tho sadly.

Back in the day here 06’ era there was a build that used 4” strips of butyl rubber layered to cover the gaps and laminated with rubber cement. That was used as a gasket between acrylic and pond liner and worked. Rubber cement works much better than ud think if u end up needing to make ur own gasket.

Im all for the “specality” silicones as a gasket as ive done those myself. U already got those holes drilled tho with a giant washer to take some pressure . I think its worth trying a rubber gasket first. Look into industrial type rubber floor mats. They come in rolls up to 100+’. Other rubber does also ive looked into it before debating if i could line an entire tank with 1/4-3/8” rubber sheets and heat weld em lol… I think itd b pretty fitting for the rest of ur one off build style ill try and find the rubber roll place for ya to check out

 

[Ianf406]

Looks like a serious build!! Never seen a steel aquarium b4

Unfortunately I don’t have the answer to your 2 queries.

I do have a question though about the choice of acrylic thickness. I am not an engineer, so just punter throwing this out there.

I have a 120”x36”x30” acrylic tank. The vertical height is 30” and the manufacturer used 1” thick acrylic. I realize the build is different in many ways, but a constant is how pressure water exerts on the structure at 36” tall. This will be a massive amount of water pressure. After installing the viewing panel will you install cross bracing to minimize flexing?

Watching with great interest

Hopefully in this picture you can see-
I have another steel piece that wold bolt down across the top. It has corner bracing like front and a center brace across the middle.

That'll be the last piece I put on!