What Is This?

Winterlily · Aug 28, 2009

Okay, these things are TINY. The biggest I've seen is about maybe 3mm, there are others even much smaller than that. They come in on plants (only from one of the LFS near me). My betta loves to hunt them. They swim super fast and sort of darting. They want to hide - even hiding on a water bubble if they can. I only see them when laying new plants out on something getting ready to plant them, or like today, in the bucket of old tank water during a water change/gravel vac. Pics below aren't great - like I said, these guys are tiny, but should be clear enough (thanks to a decent macro lens on the camera) to at least give you some idea? To my EYE, they look dark, not as "gold" as in the pics. They swim pretty straight, meaning they don't SEEM to curl that tail thing under except when freaked or dying or something. I dunno - they are teensy, and fast, so it's really hard to tell. First pic is as clear a close-up as I could get, second pic is of this thing still and nearly dying (no clue why - I just scooped him out of my water change water, but he had no where to hide), and the last is what they look like from the top while fully alive and swimming.

Close up:

Mostly dead:

From above, alive and swimming. Antennae (or whatever) and eyes etc there at the top. And for reference, that's a tiny piece of hair to the right of him. They are really tiny:

So what is this? Safe for the fish to have in the tank?? Safe for the fish to eat?? Is this those copepods (Cyclops, whatever) ?? (ETA - I just read, again, the thread on freshwater hitchhikers and these look like scuds to me I THINK? ... what do you think??)

Thanks!

Gilli · Aug 28, 2009

Looks like a Gammarus shrimp to me, commonly known as scuds. Scuds arrive as hitchhikers on plants, and live in the gravel and detritus. They are often spotted zooming and looping around the aquarium. Theyare harmless scavengers, and most fish relish them as a snack.

Winterlily · Aug 29, 2009

Okay - thanks. That's kind of what it looked like from the hitchhiker thread here too, but I was totally unsure.

Quick question if it's scuds: In reading about them online, I keep reading that any "wild-caught" scuds should be quarantined so as not to introduce various nasty pathogens to the fish. I doubt that those coming in on the plants I buy from my LFS are tank-raised as food (and so, assumedly safe), so do I need to be concerned with the fact that they are now in my tank with fish eating them?