..what do you think this is? Parasite? Critter?

They're neither snails nor planaria, I have experience with both.
 
My other thought is that they are a form of water flea. Water fleas are crustaceans and are not harmful to your fish. It makes sense because they go through a major reproductive stage in the summer. It would also mean your water is high in essential nutrients. Lucky fish. If they are water fleas, I would not worry about it... Your fish will be feasting in no time.
 
I doubt it. It seems like if it is edible, my fish would've chewed them all up by now.

This has also officially inflicted all of my tanks now.. guess that's what I get for sharing the same maintenance equipment for every tank. At this point, I'm thinking about shelling out some $50 for a UV sterilizer.. I'd imagine my head would blow right off from frustration if that didn't work.
 
Finally did a bleach test.. long story..

Anyways, it seems to have stopped their locomotion.. and just yesterday I was about to buy an Aquaclear powerhead+quickfilter combo, guess we can rule that out now..
 
I hope I get bubbles that can "do the locomotion" some day. Or even "the twist" or that butter-churn move.:woot:
 
Well, since I had already done the bleach test, there's really no reason to go on.

Now that you bring it up though, had I not forgotten about salt, I would've tried that as a treatment. But now I have a UV sterilizer on the way, I'm gonna give that a spin first.
 
Submariner UV came today.. it hasn't done any damage yet, but it'll take some time before I'll really know..

Strange thing, I'm comparing this newer model I got to the older ones, and it seems like a downgrade. Flow control was removed, and the lamp indicator doesn't seem to work.
 
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