What kind of worm is this?

[Improperbeard]

I have about three or four (that I noticed) of these worms in my tanks, attached to rocks (all rocks were pre-boiled).

Three weeks ago I got mosquito larva from my coworker from their pond, and I'm wondering if his water brought anything in.

Wondering, moreso for my own education, what these are? Are they harmless or parasitic? Would the shrimp, snails, or fish eat them?

 

[angelcraze]

It's hydra. Actually it can be harmful. Get them out as soon as you see them, but know that you can't break them or they split into two seperate hydra. Or maybe i'm getting confused with planaria. In any case, they tend to congregate on an object close to flow, so generally are close together. Maybe you could suck them out with a baster?

This article explains it well and offers some ways to deal with them.

A Hydra in My Aquarium! What Now?

A Hydra is a soft-bodied freshwater polyp that is sometimes accidentally introduced to freshwater aquariums. Here is how to get rid of them.

www.thesprucepets.com

Most likely did come in with the pond water. I personally don't chance mosquito larvae anymore, you never know what hitchhiker and bacteria comes with it from outside. But i'm sure lots of ppl do and don't have problems.

 

[the loach]

Yes that's Hydra. It would have come with your plants, take the rock out and clean it, and inspect the rest of your tank, there are probably more. It's possible your female rainbowfish died because she was stung by one.

 

[Improperbeard]

The article says fish can eat them also? That picture is highly zoomed in, so they're very small

I took the rock out and boiled it. The rock it's on is less than an inch. I'll inspect more. Would a parasite repellent like herbtanna irritate it as well?

 

[machisaki]

Yes fish do eat hydra !!! Opaline aka Blue Gourami and Mollies especially love them as i’ve had both and they straight up ate them haha !! I’m unsure if you have either. I am also unsure if any other species prefer eating them.

 

[the loach]

The rock it's on is less than an inch. I'll inspect more. Would a parasite repellent like herbtanna irritate it as well?

The problem is if they grab a fish with its tentacles it injects a neurotoxin, and the fish can get health problems and die.
Herbtana boosts the immune system of the fish to get rid of parasites on the fish, it wouldn't do anything to a hydra as it's not on the fish but it's also not a parasite.

 

[Improperbeard]

Ok, I'll just eyes out for them. I boiled the three on the small rocks. Didn't see anything on any large rocks or plants. Only thing I didn't check is the Amazonia soil, but that's because it's so heavily planted I can barely even find my shrimp lol

 

[machisaki]

Hydra will eat small crustaceans like shrimp ! Best be careful ! Good Luck !