Also make sure the bottom pane is NOT tempered (if any panes are, its usually the bottom). A tempered pane will shatter into thousands of shards (have seen this happen - cool but PITA to clean up without cutting yourself). My friends and I have cut panes of glass for baffles several times. Not too bad if you can score well and then snap. When a friend of a friend tried it with a tank, it didn't go too well. I will see if I can track him down and get a pic from that fiasco. The break curved as it broke and he ended up trashing the whole thing. BTW, he contacted a few local glass shops and none of them would touch the project, which is why he ordered a diamond glass cutter from eBay (or might have been Amazon) and tried it himself. I wasn't there but visited later to pick up a frag, just before he tossed the tank into the garbage. The only guy I know who successfully shortened his tank took the trouble to cut apart the tank first and then scored and snapped each piece. It worked but was again a total PITA project. Don't know if he ever researched trying to cut a tank that was still siliconed together.

Good luck.

Anthony

might have to try on one of the old small tanks lying around. May try the score and tile saw method. Getting a custom tank built to grow frags is really cost prohibitive.

I think I might cut the silicone down to the score line then try and snap the glass. Each piece could be snapped individually.

Thanks for the detailed info folks! Now we have a better idea of some techniques that may work & some that probably won't. Whether it's worthwhile or not will be up to the individual willing to take the chance. As I mentioned, I wouldn't try it on a display tank that I want to keep as a display, but certainly an option for a cheap sump. Once I retire the 77, it really won't be any good as a display any longer. I could always leave it at 24 inch height, but sometimes I like a little challenge.

The blade height on the tile saw is adjustable, so may even be able to use it to initially score the glass. The technique of first cutting the silicone down to the desired height is definitely a good one. Take out one piece at at time.