Divelli,

I'm new to keeping fish so learned all this from the web and my local aquarist. The worm causes bloat (they look pregnant, since mine were all males I thought that it was constipation). After a few weeks little dark threads appeared around the anus. They were very short to start with and I didn't really notice them. What I did notice is that the other guppies (which came from a different batch) kept 'attacking' the anus of the infected guppies. I later found out that some other fish find the parasites a tasty treat and can try to eat them. After a while the worms became big enough to see that they were red. This worm (camallanus) is apparantly quite rare in tropical tanks as it has a complicated life-cycle. My guppies came with it. Look for the red worm-like threads (some got up to 1cm in length). From what I understand the chances of curing them are ok if you get it early (but the worm uses an agressive hook that can often give rise to secondary infections, even after it's dead). It's not very contagious in tanks due to the complicated life-cycle. If you're sure you've got this worm, then see my posts above for the treatment.