Help me seal my tank

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canucksfan1

Candiru
MFK Member
Apr 6, 2007
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i have tried everything to seal the bottom of my tank, alot of u probably don't remember me but i got paid 20 bucks to take a tank out of some guys yard. This tank is huge roughly 420 gallons, and my problem is it has a steel bottom on it instead of a glass bottom. So i have used rust-mort to kill all the rust, and then epoxied the bottom to make sure the steel was sealed from the tank. So all of that is good, here is my problem:

The glass on the tank is not perfectly straigh with the bottom so in some spots i have to put a huge glob of silicone, this didn't really work out to well so now i am thinking of using a pond liner on the bottom of the tank, my question is what can i use to seal, or glue the pondliner to the epoxied steel on the bottom of the tank and the glass sides??? Any suggestions???
 
sounds kind of dumb, but i would just use aquarium sealant. just buy a tube or 2 and then just apply a bunch of it to the bottom and then lay your liner on top... then take a wall paper brush or squeegee. then just even out the silicon underneath.. this way it will hold it and water proof it... and if you ever wanted to take it off you can... you might have to sand the epoxy so the sealant will stick to it....

or maybe start from the beginning and reseal the whole tank again... maybe try to get a better joint with the glass and the bottom...
 
Wow, and at 420g?
This brings up a lot of questions.

Whats the make and thickness of the steel? You said it had rust on it so I assume its not stainless. It sound like someone had a piece of steel and built a tank over it.

You also said that the steel and glass where not "true" together. They never will be. The difference in expansion rates for the two and the fact that the steel is flexible and the glass is not your tank will never seal. Especially in extremes of temperature. If it was stainless it would be insane because stainless goes all over the place during temp changes.

How was it built? Any pics?

You could go the pond liner route - it may be a bit of a mess but it will make a good transition piece. I'm just concerned about the walls of the tank trying to supporting all that water with a "floating" bottom.

I would do this: Get rid of the steel and get a matching glass bottom. Strip the whole thing down and start over. Make sure the wall thickness of all the glass is right for that size tank. Build a jig if you have to and rebuild that sucker. 20 gal is one thing but 420 gal is a LOT of water.
 
I would start out with a roll of the rubber stripping used to install screen in screen door frames. Cut short pieces as needed to fill any of the larger gaps between the glass and the bottom of the tank. Once you have the bottom sealed this way as well as possible then use a single smooth bead of #1 GE silicone on the rest. You really want to avoid using anything that will perminatly bond to the serface of the glass pannels.
 
yeah i didn't make the tank and unfortunatly i don't have the money for a piece of glass that size for the bottom of the tank it is 7 feet by 3 feet, and they used 1/2 inch glass i believe, i know it will all support the weight cuz i have filled it, and the leaks don't start until it's just over half full, even if i could just put strips of pond liner from the glass to the bottom it would be good, there is silicone between the steel and the glass but there must be some small spaces somewhere, and try as i might i can't get it to seal 100%

So if i cut a couple strips of pond liner at like 5 inches wide could i use that to seal the glass to the steel if i put it a couple inches up the glass and a couple inches on the steel, and attach it with silicon or contact cement or sumthing???
 
Yeah you could. At 7x3 feet that is a long stretch. If you are going to go that route make sure the tank is well supported and do a static water test in the garage or patio for several days at least.

What I'm also concerned about is how the steel was cut - saw or shear - cut square or not - and whether it was absolutely clean when it was siliconed.

I'm not sure if the silicone will bond to the pond liner either. Dont use contact cement, it's not waterproof.

I'm almost willing to say just build a plywood tank with of one of the glass sheets and be done with it.

Good luck.
 
you could also use a strip of inner tube material over the joint if thats the way you want to go with it.
 
K well here is my idea let me know what u think
The light blue is the glass, the brown is the steel and the red is a strip of pond liner. What should i use to adhere it all together????
Oh and i know the steel and everything is strong enough because it was used as a tank for a long time, it was a saltwater tank at the '86 world expo in vancouver b.c. it had a chiller and everything when i got it but i removed all of that when i got it (i still have it all in my shed)
I'm thinking about epoxy as a glue for the rubber, then maybe another coast over top after it is on???

Fish tank.jpg
 
I'd just use GE #1 for an adhesive on the joint.
 
will that stick to a rubber pond liner???
 
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