How Often Do Sirens Sleep?

[Little Girl]

I just recently acquired a greater siren (Siren Lacertina). She's still a baby (about 5 inches long) and I was wondering how often they sleep? I've not really seen her sleeping, only resting for short periods of time and then swimming around and exploring the tank most of the time. Is she looking for food? I fed her yesterday but she didn't seem to notice it. I think she might have eaten some of it, but I can still see the chopped up pieces of worm left over