Divider Issues

I stuffed Java moss in the 1/8" gap between my dividers and tank wall.

You can also use that thick, foam, double stick tape. Just stick it in there and that'll close up the gap and it helps to keep your divider in place as well.

One drawback though is that it's a total pain to get off the glass. You'll have to scrape it off, and probably use goo-gone. If you are going to keep it divided, then you're fine, but if you want to move them around, I'd definitely do the moss.

The moss is a really good idea.

I had the same issues, the gap (in my case) was caused by the silicone used to seal the tank. What I did was cut out the corners of the divider. I think I had to cut out a 3x3 square out of the corners of the plastic canvas. I also cut the C-line, Slide n grip biding bars a little short. I used extra gavel at the bottom to make sure the hole from cutting out the mesh was filled and lowered the water line a little in the tank to make up for the hole left at the top. I have 4 divided tanks and I haven't had any problems.