500 Gallon Glass Repair or Total Loss? 6/21/11
You guys have been amazing help in the past and I wanted to run these complicated issues by you. My aquarium is 500 gallons made of 3/4" glass.
It is beyond heavy. I have the following issues and will attach photos as well:
1). Is the cross support ok?
<Mmm, likely so... though I would have had the piece of glass here extend all the way to the front pane... i.e., not had the 1/4" gap filled w/ Silicone, but the two pieces of butted glass with only a bit between>
2). Is the fracture repairable.
<Mmm, also likely. I would Silicone (tilt the tank on its side, apply weights (books) over the piece Siliconed onto the existing pane, over the fracture... an added pane of at least six inches overlap left right and up, and flush all the way to the bottom edge>
1). Take a look at the first 2 pictures and the notes I added to them.
The tank was built by Lee-Mar.
<I know these folks well. They make good tanks>
However this cross support does not look like the rest of the tank.
<Agreed>
I think the previous owner may have rigged this cross support up. Despite the fact that there is a 1/4" gap between the cross support and the inside edge of the front and back panes of glass, it looks like there is enough silicone and glass sandwiched together support the weight of a continent or two...lol. Does the cross support look sturdy to you?
<Again, I wish there was almost no gap here. IF you have occasion to cut this away, get a closer fitting piece>
2)....the more worrisome issue. This fracture is my fault. The forks on the material lift I used to move the tank rubbed against the bottom of the front pane of glass causing a 1.5 inch clam shell fracture. The fracture does not appear above the bottom pane or into the water line. It extends from to bottom of the tank to no higher than the thickness (3/4") of the bottom pane. This makes me think that the integrity of the glass is not compromised to the extent that the tank could burst.
<Hard to say... one does NOT want any line fractures in this area>
However it did slightly break the main silicone seal between the panes of glass. I water tested the tank and it was ok until I got about 300 - 350 gallons in it.
The pressure of the water caused a slight drip. Surprisingly it did not leak out of the front of the tank at the bottom where you can see the opening in the glass.
<Not surprising actually... the water will exit from wherever is easiest>
This opening was finely crushed/powdered glass shards that I had removed. The leak was actually coming from the bottom of the glass between the front pane and the bottom pane. However the bottom pane of glass is not damaged so the leak must be coming through the silicone.
<Yes, around a seam>
The fracture must have broken the silicone seal here just a little. Replacing the front panel is cost prohibitive and the glass would be over 400 pounds making it an impossible job to do in my garage. I would have to take it to a shop hundreds of miles away. This means I can never reseal the silicone *between* the glass. However I can reseal the silicone run along the inside corners of the bottom and sides of the tank.
<And the outside with the added pane>
Would this create a permanent enough seal?
<Hopefully so>
I was also considering laying a small square piece of glass on the bottom piece of glass and siliconing it to the front inside pane just above the fracture.
<A useful approach as well... making the front the back of course>
This means I would have the new silicone seal and glass sealed to the front panel maybe strengthening this area a little and sealing it off better. I was then going to pump silicone
or epoxy (do you know of a good brand or will silicone suffice?)
<Just Aquarium Silastic/Silicone>
into the open fracture just above the bottom plastic piece as seen in the photo.
<See above... with a pane over all this work, extending a good half foot plus left, right and above>
This opening is very small, maybe a millimeter tall and half an inch wide and obviously not deep into the glass. There is no leaking here but I want to reinforce this area. What are your thoughts? Repairable without replacing the glass?
<I do hope so>
I want to set the tank up in my house but if there is any doubt that this fix wont work forever then I will keep the tank in my garage where it will do less damage should it leak.
<... OR kill or injure someone should it rupture>
I also read that to remove the current silicone run along the inside edges of the tank I should use a solvent. If this is correct. what kind?
<... Sharp single edged razor blades and likely Toluene>
If I apply too much solvent, could it leak between the panes and deteriorate the silicone between the glass?
<Apply it/this organic solvent with clean paper towels, only slightly dampened, only to the areas where the old Silicone has been cut away. You do NOT want it to pool>
If so should I just stick with a razor blade and no solvent? Thanks for your assistance with this. The damage to my tank makes me nauseous and I pray I can fix it.
<Worth trying. Do take your time here. Bob Fenner>

Re: 500 Gallon Glass Repair or Total Loss? 6/22/11
Thank you for the fast response.
<Welcome>
So it sounds to me like there is no guarantee this will be a permanent fix but it "should" work in theory.
<This fix is permanent. It will work or no>
I have attached another image for clarification. The image is a cross section of the tank. The blue areas being the front, bottom, and back of the tank.
The red pane on the inside of the tank was what I was thinking to do. If I understood your response correctly, you are saying to add the outer (red) piece of glass and have that extend 6 inches up, left, and right?
<Yes>
If so, how thick would you suggest these extra panes to be?
<Best 1/2". BobF>