Can you see the little white bits in the glass They look like lines but they are moving I am having a terrible snail problem, are they going to grow into snails? Would a better filter help Its a cold water tank with minnow in it TIA
They look like they might be planaria (flat worms). Most of them are harmless, especially to adult fish, but they indicate a possible dip in water quality and probable over-feeding. If you cut down on feeding a bit and give the gravel a good vacuum then that will help, and it will cut down on the snail population too.