So i was thinking about using sand as the substrate since i thought maybe the BNs would like to dig around in it, but now i guess not? I don't trust myself with the chopstick idea. Are they fine on just bare bottom? Or should i have gravel? In my 20 gal i have gravel and plant mix for the substrate but in my 75 i have bare (turtles and koi fish plus gravel seems a little annoying for cleaning?) but i haven't been doing fish long so i'm not sure which would really be better? Right now i have a bare bottom breeding tank planned but if people think gravel will help i'd get some? What size gravel is best? Thanks!