Reptile & Amphibian Forums

As part of a population study, I'm keeping a wild-caught greater siren in the lab to test a marking technique (fluorescent elastomer) and make sure the marks stay visible. However, I'm having some trouble getting it to eat and wanted to see if anyone has any suggestions.

The siren is about 12" long, in a 65 gal. tub with ~55 gallons of water in it. There are plenty of terra cotta and slate cover objects, plus masses of aquatic plants like southern naiad and duckweed. The substrate is small gravel; would sand be better? How difficult is it to clean a tank with a sand base?

Also in the tank: a small group of mosquitofish, many freshwater shrimp, 3 small crayfish, snails, small diving beetles and mayfly larvae, and 2 brown hoplos that are 4-5" long (Hoplosternum littorale, an exotic armored catfish). I'm trying to give the hoplos away because I think they might be competing with the siren for pieces of worms, but nothing in the tank seems to be bothering the siren too much or picking at its gills. The siren was collected from a roadside ditch in Myakka River State Park here in Florida (with research permits) and the fish, inverts and plants were also collected from nearby habitats.

I had hoped the siren would eat the fish, shrimp, crayfish or snails, but from reading posts on Caudata.org, I guess that's not very likely. I've tried feeding it freshly killed freshwater shrimp, earthworms (both whole and pieces), and some shrimp paste that other people were feeding to freshwater fish in the lab, but I haven't observed it eating yet. In fact, the siren actively flees when it bumps into a moving piece of an earthworm. Should I try trout chow or bloodworms next, or maybe feeding it in a smaller, separate tank?

Thanks for any suggestions on changing the enclosure or the food!
-Sarah

(The pictures below should show the siren under some terra cotta pieces, then the ditch I collected it from, and then pictures of the tank setup.)

Additional tank picture

My lesser sirens were also finicky until I offered them frozen bloodworms (available at most pet shops). They took to these immediately. They also eat live amphipods and isopods, and occasional ghost shrimp.

I've tried earthworms, but the sirens usually spit them out after attempting to ingest them; I think it may be the length of the worm that bothers them, as they can't get it all the way down in one gulp.

I forgot to mention: sirens will take in small pieces of gravel with their food; they usually spit them out, but they probably do end up swallowing a few. I don't know if sand would be more or less problematic than gravel in this respect. I just sink a shallow watchglass in the tank and put the bloodworms in it with a turkey baster. The siren scatters some up into the water column, but the killifish I keep with him eats all those.