Help!! frag tank problems

I've heard of people using epoxy to mend acrylic at the seams, but it doesn't help the aesthetic side things.

 

I'd try to remove the silicone and reweld with weld-on 16. Weld-on 16 isn't the strongest but as long as the frag tank isn't super tall I don't think you should have a problem (it is certainly a more appropriate solution than silicone). Weld-on 16 is a syrupy consistency and should allow you to fill any gaps in the seams. You should be able to just let a bead run down the seams without creating too much of a mess. Weld-on 4 is what I would use if putting a small frag tank together from scratch but it's super thin and wouldn't do well at filling gaps.. the acrylic needs to meet pretty perfectly. Weld-on 40 is quite strong but it is super thick and would be a huge mess and I wouldn't try it for this purpose.

If you're concerned with aesthetics and aren't comfortable with working with acrylic I'd probably try to find someone to lend a hand with this. If aesthetics aren't too much of an issue, I'd say get some weld-on 16 and have at it... maybe practice a little with some scrap acrylic first to get a feel for the consistency and timing.

 

I've used this stuff before. McKanica® Silicone Caulk Remover Gel (0354) - Pure Silicone Caulk - Ace Hardware There was a removal product by DAP for silicone but I don't see it for sale in the US anymore, unless they rebranded it. I used that stuff once years ago on a thick acrylic window I needed to pop out to repair the frame. It took a few hours but dissolved the silicone to where I could pull it off. The McKanica stuff I just recently used to dissolve silicone caulk around a tub I was having problems with.