# Putting a new glass bottom on a tank



## KhuliLoachFan (Mar 8, 2008)

I got that tank on craigslist that had a picture of the bottom cracked. The fellow has completely removed the bottom plastic trim and all the broken glass is gone. The sides were re-siliconed with some black stuff. It all peels away easily.

What I don't know is:

1. what kind of glass to buy. It looks pretty thick from the sample piece I have which is 6mm thick (taken from the original tank bottom).

2. does the new glass bottom go inside the side-walls of the tank, or below them? (inner dimension or outer dimension).

Any tips? I have never done this before and I got this mostly to learn how to do a tank repair and re-silicon.

3. Where to buy a larger quantity of aquarium silicon than the little tubes they have at Big Als.

W


----------



## bae (May 11, 2007)

KhuliLoachFan said:


> I got that tank on craigslist that had a picture of the bottom cracked. The fellow has completely removed the bottom plastic trim and all the broken glass is gone. The sides were re-siliconed with some black stuff. It all peels away easily.
> 
> What I don't know is:
> 
> 1. what kind of glass to buy. It looks pretty thick from the sample piece I have which is 6mm thick (taken from the original tank bottom).


Get the same or greater thickness. New glass can be very expensive. If you go to a glass shop (the kind that makes and repairs store windows, etc) and ask them to cut a piece from their scrap pile, they'll sometimes only charge you for the cuts, or a nominal price. You might phone first and find out when they aren't busy.



> 2. does the new glass bottom go inside the side-walls of the tank, or below them? (inner dimension or outer dimension).


For tanks that size, the sides rest on the bottom, so it's the outside measurement. If you have the original plastic trim, you can take it along to make sure the new piece fits. If you don't, you can be a little more relaxed about dimensions. You can buy plastic trim, although not in black, for a few bucks at a building supplies store. Get the plain right angle stuff. It's there basically just to protect the edge from chipping.



> Any tips? I have never done this before and I got this mostly to learn how to do a tank repair and re-silicon.
> 
> 3. Where to buy a larger quantity of aquarium silicon than the little tubes they have at Big Als.


You can buy silicone caulking at Canadian Tire and other building supplies stores. You'll need a caulking gun, but these are only a few bucks. Read the labels carefully and avoid any that is labelled for kitchen or bathroom use. These have mold inhibitors which can be toxic to fish. See the current discussion here about silicone caulking for marine tanks for lots of info and opinions. Ideally, get stuff labelled as aquarium safe, but often the manufacturer doesn't want to take the risk of labelling a perfectly safe product for liability reasons.

As for the rest of the tank, remove any loose caulking, clean very well, and replace. It's really only the silicone between the panes of glass that provides the strength.

There are a lot of articles on the web about building and fixing tanks, and there's more than one 'right way'. There's one with photos on pricenetwork in the forum/aquaria/articles section.

I've mostly only replaced glass in smaller tanks. I hope the more experienced can give you better advice.


----------



## bob123 (Dec 31, 2009)

*new glass bottom*

Hi; Where ever you by your silicone make sure it is safe for aquarium use. I buy my silicone at Home hardware and also buy glass there. The bottom piece of glass goes over the sides and ends outside measurements. Make sure you clean all the glass surfaces completely before you silicone anything.
good luck.


----------



## 50seven (Feb 14, 2010)

KhuliLoachFan said:


> I got that tank on craigslist that had a picture of the bottom cracked. The fellow has completely removed the bottom plastic trim and all the broken glass is gone. The sides were re-siliconed with some black stuff. It all peels away easily.
> 
> What I don't know is:
> 
> ...


You filthy bastard! I was emailing him for it, LOL!

As far as silicone goes, 100% silicone is, well, 100% silicone, and when it's cured, it will not leech any chemicals into the water. Allow it to cure for about a week before you fill the tank, and any residual chemicals will dissipate during the cycling process. I have not done this yet myself, but from my experience in the construction industry, fully cured 100% silicone IS considered food grade, so it would also be safe for aquariums. Get it from Home Depot, just make sure it says "100%" silicone on the tube.

Cut your bottom glass in such a way that when it is put into position, the silicone will not be holding up the sheet of glass and therefore bear the weight of all the water. The silicone will seal it, and will hold it in place for a while, but won't be sufficient to bear the full weight of all your contents over time.

But hey, if you can't figure it out, you could always give it to me...


----------



## KhuliLoachFan (Mar 8, 2008)

Hehe. 

W


----------

