For quite some time now some of the fish in my 25 gallon tank have had long, red, thin worm-like things protruding from their back ends. I thought that they were callamanus worms but after treatment they have not gone away, in fact there are more now.. Please help me to identify them and tell me if there is anything that I can do. The pictures are of my red guppy, who is the worst. The pictures don't do much justice but in real life there are about 4 or 5 of the 'worms' and they are red in colour. The longest is about 4mm long.