White Spider-like creatures on side of tank

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SEInverts

Aquarium Advice Apprentice
Joined
Oct 5, 2010
Messages
12
Location
South Florida
Here's the background:

The tank is in a screened porch in South Florida and was started three weeks ago. I had "low-light" plants so I didn't have a light on the tank...these plants died (inevitable, I know) and I tried to get as much as possible out. Don't worry, I've done WCs since then.
On Sunday, I got some plants (guppy grass?) and some red cherry shrimp from a local guy (not store) who had them outside. Now that I've put the shrimp and plants in the tank, I have these small white spider-like creatures on the side of the tank. My first reaction is that these are tiny baby shrimp (a couple of the shrimp were berried) but they're SOOOO small that I can't tell what they are. They look like spiders and as far as I can tell and do not have tails (which I believe the baby shrimp would have). I've looked up some baby shrimp pictures online and I'm pretty sure that's not what this is.
I'd post a picture, but they're so small you wouldn't be able to see it with my camera. I've googled all kinds of things and haven't been able to come up with anything.
Anyone have any ideas? They're not worms, but tiny spider-like creatures with 6 legs that stick on the glass. Thanks!
 
Welcome to AA!

Are they hydra? link: Hydra

That has pretty good pictures of hydra. You can remove them manually (scrape them off the tank glass with the business end of a gravel vac), let them hang out if you don't have fry and don't mind them, or go with a more radical method of removal.
 
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Do your things look like the picture I have attached below? If so, then they are definitely hydra. And hydra are something you absolutely don't want in a shrimp tank, as they will kill baby shrimplets, and will annoy (sting) the adults, which will be a source of stress to the adult shrimp.

Unfortunately, mere physical removal of the ones you see is probably never going to be enough to totally remove them from the tank. Your best bet is to treat the tank with either liquid or powder form of fenbendazole.

In powder form, you dose at the rate of about 1/10th of a gram per 10g of water. Dose, wait 48 hours, dose a second time. Problem solved. Kills hydra (as well as planaria, nematodes, and other such critters) in the tank but is perfectly harmless to shrimps. You can get fenbendazole in most pet stores (usually in the dog section, as it is sold as a dog de-wormer) or online. It is sold under several brand names, I think Panacur is the most common. I bought some powdered Panacur about a month ago on ebay for under $10 shipped, in order to treat one of my shrimp tanks that had hydra due to me putting plants in there I got from someone online (and, unknown to me, had been kept outside).

If you do a Google search for "fenbendazole" and "shrimp tank" you should get a lot of hits that discuss it at length.
 

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