What does it mean if fish starts having white poos?

let's back up here a minute.... you should not ever see poo hanging off the fish or on the bottom of the tank. if you do.... this is a clear sign of OVERFEEDING.... way overfeeding! Fish waste should be liquid and quickly dissipate into the water upon discharge. clean your gravel, do several 30% water changes over the next several days and feed once per day only a very flakes per fish and do not grind it up in your finger tips... just drop it in. overfeeding is the #1 killer and problem with aquariums.