Wow, that looks real cool.. I did the same for a cave with stones, driftwood, and lots of gravel (mine is mixed black and white also), but I have fake plants. The cave is for my BB (betta boy). There are little crevasses and a tunnel that he can hide in and swim from one end to the other. I also put a lot of gravel on top of the tunnel. I really like your fish tank. It looks awesome.....Can't wait to see what the larger tank holds in store.....:clap: