Help ID an external parasite, please!

[Lutefisk]

I have an A. borellii male with a case of some external parasite (photo below). There are small, worm-like things on his sides and fins. When I first noticed them, they were no bigger than a microworm, but now the biggest ones are much thicker than that. They are on the surface of the fish, rather than beneath the skin. I've never seen one move. There isn't any obvious irritation at either end, and there are no prongs at the end like the pics of anchor worms I've seen. The streaks in his tail might actually be fin damage--he was sold to me as part of a "trio", and has since been separated from the dominant male.

What are these things? If I can't identify them, what treatment would you recommend I start with?

Thanks!

 

[Mike Wise]

Probably flukes. Several products will kill them. Formalin will do the trick but is a known carcinogen, so I don't recommend it to inexperienced people. Many of the organophosphate insecticides will work, too. I suggest you research fluke treatments in a book or on line.

 

[gerald]

They could still be anchorworms too ... not all kinds have the paired egg sacs. I didn't realize there were external skin flukes large enough to see without a scope. Either way, the treatment should be similar.

 

[Lutefisk]

I'm reading that praziquantel has supplanted formalin or organophosphates as the go-to treatment for flukes, and that it should be effective against anchor worms too. I'm in luck--both prazi and formalin are already in my cupboard, so I'll let you know how it goes. Thanks for the advice!

Here's a link to a web source I like to use for anyone with a similar problem who stumbles across this thread.

 

[Lutefisk]

Update: I've been dosing PraziPro per label directions, but some parasites are still visible on my borellii. The Danio margariatus he shares a tank with don't seem affected, though.