So i found a worm peeping out of my substrate.Didnt wiggle, didnt move,just stayed in one spot.As soon as i put my hand in the water , it quickly went back into the substrate..I have never seen any worms in any of my aquariums, and I cant find any information on this one. It had to be long, around 2mm wide,it stuck out of the gravel around 1/2 inch. Was creamy white with red rings around it. I syphon the gravel and do wc's weeky.never over feed..What can this be?