i had a tank full of them before. all i did was scrub the rock with a tooth brush daily for about 2 weeks sucking them out as i scrubbed. i also dropped in some fresh carbon every otherday because of the die off i was creating, did not want to feed what i didn't scrub off. it went away, i think more because it can not take the daily scrubbing. nothing eats it, so its not use to being relentlessly bothered like that. i did not give it a chance to recover. thats my theroy on it.