Yes I did - even for such small tanks, I ended up using nearly 3 tubes of GE Silicone 1 for each tank. Be forewarned, the smell will take your breath away! I pumped the silicone out of the tubes and smoothed it out with an old credit card - when done I had a thick pad of silicone about a 1/4" thick. Then I tipped the background into the tanks bottom first. You have some wiggle room before the silicone starts to set up. (I made my backgrounds so they were a 1/2" smaller than the back glass). I had enough silicone so I could run a bead in the 1/2" gap from the foam to the glass corner - like a beefed-up corner seal on a tank. It has held up great. I'm getting ready to start a background for a 55 I have, and maybe a 90 if I get lucky (my coworker's son wants to get rid of his 90g). I can't wait to start. I learned a lot from making these two and I have things I want to do differently for the next tanks in regards to rock shapes and doing a darker color. I find the fish can get washed out & lost on the light color I used. I've already drained the top tank and I will go back and repaint it darker with more tinted Drylok too.