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Discussion Starter · #1 ·
This is my first time contributing to the discussion board, but have read through many a thread with much interest.

I daydream much about monster fish tanks full of African Cichlids. I've built a few fish tanks, a couple all glass (a 90g & a 50g), a plywood & acrylic (about 530g), and the the latest, a steel 357g with a glass front. Inside dimensions are 108.25"x28"x27.25"

I scored on the sheet of 1/2" glass for free from a construction buddy, I weld, & have built a couple of steel water tanks out of 12 G galvanized sheet metal, and got the idea to build a steel fish tank. Not galvanized, but epoxy coated steel. I actually built the tank about 15 years ago, kept it in a greenhouse and mostly housed native fishes in it. The tank is not in use at the moment, but I am wanting to get it going again, which brings us to what this topic is actually about.

The tank is built out of 12g steel, back, sides, & bottom, with an 1/8" x 2" flat frame around the front and top. I had 3 equally spaced (removable) cross braces on the top. Overflows built in similar to bulkhead fittings but welded in. Interior was coated with 3 coats of epoxy paint, exterior metal primed & painted, then glass sealed in with silicone.

Tank worked great, simple to build, strong, reasonably light weight, not too much expense. Trouble is, soon epoxy paint started peeling off the interior. I noticed blisters about 1/2" to 3/4" forming in the paint. Tore tank down, spent brutal hours removing paint and re-doing with another product, and it happened again. Tank has actually been sitting for a couple years and most of the paint has literally fell off the inside. Now it is rusted and will have to be wire wheeled down to bare clean metal again.

Anyone have any ideas on a product I should try? I researched products before and followed instructions on the application. Paint store actually gave me the epoxy I used for the second go around along with much apologizing & head scratching.

There has to be a product that will stick well, hold up to UV light, be waterproof, and non toxic. I know steel water tanks are coated with some type of epoxy. Any ideas?
 

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well...nothing lasts forever, especially with steelconstructions overall, it constantly needs updating, repair, etc to keep it as new.
i dunno, an idea i just got was is to try using a pondliner instead of paint. i dont know if it can be sealed to the glass with silicone though.
 

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I would use a good primer for a metal boat (not anti-fouling) or steel roof, then two coats of gloss white Palgard, and two last coats of gloss black Palgard.
 

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We have steel tanks that are exposed to water at work. Whenever we get a new tank, we have to let it be exposed unpainted for about a year for the oil to leach out of the metal. We then sandblast the rust off and prime and paint it and the paint lasts 10 years.
 

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Discussion Starter · #6 ·
Mcdaphnia said:
I would use a good primer for a metal boat (not anti-fouling) or steel roof, then two coats of gloss white Palgard, and two last coats of gloss black Palgard.
Thanks, I actually used Palgard but without primer as I was instructed by the paint company. Why gloss white, and then gloss black? I used blue before, wouldn't mind trying a deep green this time, but black would be ok.

Interesting what tannable75 had to say about oil leaching out of the metal. It does seem that there was something on the metal that kept the paint from adhering. I can't imagine having to wait a year before painting though. I took care to clean the metal, and to rough it up beforehand. I was told primer would be unnecessary when I bought the paint.

I hate to go through this again, but it will be worth it to have the tank up and running.
 

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Discussion Starter · #7 ·
fishwolfe said:
how about powder coating it?or maybe a ceramic coating like www.lizardskin.com ?
Haven't looked into powder coating yet, but looked into lizardskin coating which sounded promising, but when I called the company for more info they said their products were not for continuous submersion.
 

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The old Cleveland Aquarium had a number of concrete and plywood tanks and a few steel tanks painted with Palgard. There were some steel fittings on some tanks that were also painted with Palgard.

The first reason for two coats of white and then two of black is that the white has nothing added and so is the strongest color. then the outer black coats contain a pigment that blocks UV, protecting all the paint layers. A second reason for using two colors is that if something scratches or chews it way through the paint (plecos!) you can see the color change and take it as a warning. Note: The color change may be the obvious one on the tank walls and bottom, or it may be more subtle, in the color of the pleco poop! Or is that less subtle??

I talked to my brother-in-law about the tank. This is a guy who had years of work experience with metals for aircraft and rockets. His hobby is restoring cars when he's not tending his fish tanks. He said the first thing is to test the tank with a magnet. If it sticks, the tank is rolled steel. If it doesn't the tank is 300 stainless. 300 stainless takes a different kind of primer. If the welds and the steel are different, that could be a problem but since this tank didn't fall apart on filling, it is not going to apply here. He thought the glass window should be removed. Otherwise there could be rust hiding behind the gasket and the glass could be damaged by the cleaning work on the steel. The primer should be compatible with the paints used. Getting both from one company that pairs them off is the best bet. Before priming, use a lacquer thinner to remove any oils on the steel from tools or hands. Research: steel boat primers for under the waterline. The paint should match the primer which should match the type of steel. He said an automotive primer should work too if it matches up.
 

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Discussion Starter · #9 ·
Thanks McDaphnia,
I appreciate the advice and the effort. When I bought the steel I bought cold rolled steel, not stainless, and anyway it is now covered with a layer of rust so it sure ain't stainless.

I talked to a welder friend and he said he has seen similar problems due to the oil the manufacturer coats the metal with to prevent rust. He told me they use the same steel for water tanks which they primer and then epoxy coat, but they sand blast the metal first.

I'm going to remove the glass and have the tank sand blasted then follow your advice on primer and paint. If that doesn't do it I don't know what would.

I may decide on some fitting changes in the meantime while it is torn down.

Maybe I need to start a new topic with this but I would like to hear some input on what size and the locations of the thru the tank fittings that ought to be in place. I had a homebuilt trickle filter under the tank in the stand before, but it sure was noisy. I prefer the drains to be thru the top rear of the tank rather than stand pipe type overflows on the interior of the tank because most of the hardware can be hidden behind. Top back drilled tanks don't seem too popular though for some reason.
 

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Another thing he could try doing since the structure is strong would be to line the tank with some kind of thin wood coated with two part epoxy like west systems.

He would in no particular order...

coat the wood with the epoxy
silicone the wood pieces to the inside of the metal tank
silicone the glass back in
and then once all the wood was in silicone the joints

Just a thought.
 

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Discussion Starter · #12 ·
So far, due to other obligations I haven't started on repairing the tank. I'm in the middle of building a new home.

I have considered lining the tank with plywood, then painting with epoxy, but I think there would be a problem fitting the glass back in with the added thickness of plywood. When I get started on the project I plan to remove the glass and sandblast the metal. I will better be able to see what kind of clearance I have then. I might be able to use thin plywood like 1/4" or 3/8" but I could wind up with an issue of a slight flexibility of the plywood if it wasn't perfectly tight against the metal. Maybe doable though if I'm careful.

I'm hoping with sandblasting, proper primer, and with enough coats of epoxy I should be in good shape.

One odd thing I noticed was that the cheap Krylon spray paint I used on the exterior has stood up well, even with it exposed to sunlight in a greenhouse. I believe I did use a cheap metal primer on the outside before painting. I don't know if the primer was the key, or the fact that it was not submersed.
 
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