Reptile & Amphibian Forums

Hello,
I've got a musk turtle inside of a 20 gal tank that is filled about 5 inches high with water. I don't have any plants in there, but there is a lot of green algae that is already starting to accumulate on the pebbles and rocks and stuff. Lately I've noticed some tiny roundish bugs swimming around at the bottom in or around the pebbles and rocks. They are too small to really take a picture of (about the size of the tip of a marker). I'm new to aquatic tanks and I'm just wondering what these bugs are, what their purpose is, and if they have the potential of being any harm to my turtle. I am assuming these bugs are like tiny tiny dung beetles that feed on the excrement and detritus at the bottom of the tank. Anyone know? Also they are kind of bluish in color (very tiny)
Thanks,
Mark

1 Razorback musk (dilberte)

Observing them closely, do they appear to move by kicking their back legs and do they come to the surface to breathe? If so, they are may be juvenile Water Boatmen (they start small and grow a bit), which are true bugs in the family Hemiptera. They could also be small Crawling Water Beetles (this is the common name) if they simply crawl around slowly. These do not increase in size once they transform into adults. Water mites, which are arachnids, are round and small but are usually bright red in color. Daphnia or Water Fleas are tiny crustaceans, but they usually move up and down in the water column using front legs. One very high probability is that they are Ostracods, also tiny crustaceans with tiny clam-like shells. These are ususally pale brown or tan, however. Check them out under a powerful hand lens and look for more details. also, check out pictures of the above on the web.

Hey thanks for your help, I'm pretty sure now that they are "Daphnia," they seem to fit that general look and description. They are definitely more crustacean like, and have more of the daphnia/water flea description, with the translucent carapace and barely visible head. According to the information I've found, Daphnia are harmless and actually benificial in that they feed on stuff like algae and bacteria and some of that other organic mess that's in the tank. I'm just wondering how they got there in the first place, cuz it's almost like they just popped out of nowhere. I've also read that they are parthenogenetic. Interesting.
Thanks again,
-Mark

They came in with the moss as juveniles or "winter eggs". I would still bet they may be Ostracods, however.