I keep finding more and more stores in my area that sell feeder guppies, and I was really happy about that until this week...

I've been to four different aquarium or pet stores this week (some with very good reputations, some not so much) and every single one of them had a tank full of guppies with large beige/pink growths on them. And I mean really pretty large - over 1mm diameter and sticking out 1mm from the side of a guppy that's only 3mm across the shoulders. The growths can be anywhere - head, gills, body, tail. Not on the fins, though. And usually just 1 per fish, sometimes 2. If they're in a pigmented area they can be pigmented, too. At first I thought it wasn't affecting the Endler's livebearers that are invariably mixed in with the guppies, but today I found an affected Endler's. I suspect all of these shops use the same distributor, but I didn't ask any of them yet. Last week the one store I visited did *not* have cysts on their fish, so it seems to be a problem specifically with this week's delivery.

Long story short (or not, I guess), it's some kind of encysted worm. I tried to pull off one of the growths from a fish I'd frozen, and it unraveled into a 4mm long yellowish worm with kind of a small clear sac at one end. They seem to be fully embedded in the skin, not stuck to the outside like an anchor worm. Freezing killed it so I couldn't see how it moved.

So I wanted to caution anyone who buys feeder guppies, especially in CA I guess, to be on the lookout. It's really hard to miss, especially if you're looking at the whole tank of fish. They may be safe to feed after freezing (freezing killed the worms, but I don't know about any other life stages that would be in there), but that obviously defeats the purpose of buying live prey.

Also, I was hoping to take advantage of our wide geographic distribution. Any of you who buy feeder guppies, have you noticed this problem at your local store? If you're comfortable asking, I'd love to know your store's distributor (whether your guppies have the cysts or not) to see how pervasive this problem is - I think I read elsewhere that most of the feeder guppies sold in the US are from one large farm, but I've got no idea if that's true.