I make a slurry with dry filter food and tank water, then use a pipette to target blast it into rocky surfaces and crevices. I figure that grows a biofilm. Got my Fromia two years ago. It was skinny and starving from being in LFS tank for six months. My tank was only a few months old at the time, but he fattened right up using this approach. When the tank was new, I treated the rocks every three days. These days I don't bother since the tank is mature.