i bought a fish from a local fish keeper and when i netted it and introduced it to my tank i noticed as soon as i put the net in that some nematodes had came off the net. the fish was a peacock bass about 6" so still a baby i didnt see any nematodes in the bucket however the bucket was white. this was about a year ago and at the time i had black gravel and the nematodes got more and more in the end i took all the gravel out and the tank was heaving with nematodes all my local fish stores didnt know how to get rid of them. eventually and up to date they gradually went or dies off with plenty of tank maintenance and regular water changes i do still have the odd one swimming about. has anyone else had problems with nematodes ive heard levamisol is good to removed them but ive not tried it.