Okay, now that you have done that, I fear you have a serious problem on your hands. The tank is, I'm going to presume, acrylic (plastic) because glass would very likely have exploded if bowed out to 1/4 inch. The light falling in it would have been the least of your problems. (although to answer your question, if it wasn't plugged in it would have done nothing. Let it dry out and it should be fine.)
Sounds like somebody has modified this tank, in a very bad way. If it was built with a support brace across the top this was there for a reason, ie to hold the front and back together. Sounds like you are going to have to figure out a way to re-brace this before you put the full amount of water in it. If it's bowing out at 3/4 full it will shatter with more pressure on it.
This does not mean the whole thing is useless or has to be thrown out even if there is no practicable way to brace it enough to fill with water. You could probably make it work as a paludarium although that would be a considerable design challenge for you. You could still keep fish in the bottom portion of such a setup although maybe not as many as you have now. That is a problem for the future though.
I leave it to the more experienced DIY and aquatic engineering types here to advise you further. Best of luck with your tank.
Sounds like somebody has modified this tank, in a very bad way. If it was built with a support brace across the top this was there for a reason, ie to hold the front and back together. Sounds like you are going to have to figure out a way to re-brace this before you put the full amount of water in it. If it's bowing out at 3/4 full it will shatter with more pressure on it.
This does not mean the whole thing is useless or has to be thrown out even if there is no practicable way to brace it enough to fill with water. You could probably make it work as a paludarium although that would be a considerable design challenge for you. You could still keep fish in the bottom portion of such a setup although maybe not as many as you have now. That is a problem for the future though.
I leave it to the more experienced DIY and aquatic engineering types here to advise you further. Best of luck with your tank.