Small leak on the bottom of my 75 gal acryllic tank

[Jayjangle]

Hello all. I'm finally going to set up a used 75 gallon aquarium tank I bought used a couple of months ago. I am currently running a second water-test by filling it with hose water and allowing it to sit a couple of hours to ensure it wont leak when I set it up inside.

I am noticing a small leak under the tank in the left corner. The previous owner made a sort of chamber to hook hoses to in that corner (not sure what the specific purpose of the chamber is), and it appears that the leak is occurring from this alone due to some small cracks.

I'm wondering what the best approach is to fixing small leaks like this on the bottom of acrylic tanks. Not sure about types of sealant I can use; I went to my LFS this morning and they do not carry acrylic sealants and were unsure about what to do as far as acrylic aquarium leaks go. Does sealing differ when a leak is occuring on the bottom vs. the corners and walls of the tank?

 

[Smitty]

Could you be describing a built-in overflow? Is it leaking from cracks, or a bad silicone seal? You don't want to fill this tank if there is a leak and if there are cracks on the bottom, you are asking for trouble later on. I would drain it down immediately now that you have found a problem.

 

[Jayjangle]

Could you be describing a built-in overflow? Is it leaking from cracks, or a bad silicone seal? You don't want to fill this tank if there is a leak and if there are cracks on the bottom, you are asking for trouble later on. I would drain it down immediately now that you have found a problem.

Hey there, thanks for the response. I just got done draining it and I inspected the bottom. Yes, I do believe the chamber is an overflow. Honestly I can't tell for sure if it is a bad silicone seal because I notice the leak occurring directly under the tank, not where the seam/seal is, but then again it was such a small leak that it might be hard to notice there anyway.

One thing I noticed after looking more closely at the bottom is some sort of hole that was drilled in the bottom and then sealed off with a small square of acrylic from inside the aquarium. I'm thinking that this was more likely to cause the leak since I could not feel the cracks in the overflow from the outside of the tank's bottom.

One thing I considered was measuring the length and width of the tank and getting an acrylic sheet to fasten to the entire bottom of the tank. Good or bad idea?

 

[Smitty]

Ok, what you are describing is a built in overflow normally listed as "reef ready" for a tank. It sounds like the previous person didn't use it as such because it is sealed. It also sounds like it wasn't sealed correctly if he put a patch piece right there, normally it would have been sealed with a bulk head of some kind.

You can always get a piece of acrylic for the bottom. Are you talking about replacing the existing, or putting it down over the top of the existing? Replacing is the best bet, but the cost will go up. If there is any crack though, that is the best bet. I would hate for something to happen and then you end up with 75 of water on the floor along with all the inhabitants.

Can you post up a picture?

 

[Jayjangle]

Ok, what you are describing is a built in overflow normally listed as "reef ready" for a tank. It sounds like the previous person didn't use it as such because it is sealed. It also sounds like it wasn't sealed correctly if he put a patch piece right there, normally it would have been sealed with a bulk head of some kind.

You can always get a piece of acrylic for the bottom. Are you talking about replacing the existing, or putting it down over the top of the existing? Replacing is the best bet, but the cost will go up. If there is any crack though, that is the best bet. I would hate for something to happen and then you end up with 75 of water on the floor along with all the inhabitants.

Can you post up a picture?

Unfortunately, the camera I have been using is not working, so I can't post a pic at this second. I will see if I can get one uploaded later. In fact, I would say count on it, I really want an accurate opinion.

I was talking about putting a piece of acrylic under the bottom and fastening it with some sort of sealant. I don't even know how I would replace the bottom; it's a scary thought to me since I have never worked with acrylic and don't want to break the tank trying to get it off. If it doesn't sound to hard I will go ahead and do that. Would there be another kind of material I could use to do this that would be better?

Also, when I do get this fixed one way or another, is there a better option for leak-testing than filling?

 

[Smitty]

Leak testing by filling is the only option. Best done in a location that can afford to have a lot of spilled water (like a garage or outside).

I have no experience with replacing a bottom or anything but I would guess the best bet if you aren't removing the bottom is to put a new piece on the inside. Putting it on the bottom really won't do as much. When putting on the inside you can do a better seal.

Of course, when you are putting another sheet in, you are going to make that a nice and heavy tank. I would would also guess, and I stress the guess part, that you wouldn't need to have as thick of a piece because it isn't going to be the main structural component.

I would replace with the same material the tank is made out of. It would be better at getting a good seal between the materials.