What are these little guys?

[utahsaltreefer]

There are probably about a hundred of these guys all over the glass of the tank. Sorry for the poor picture, but they are tiny. Only about 1/8 of an inch. They vary between having 6-14 arms.

 

[Anonymous]

I'm guessing they're some type of cnidarian in its polyp stage. It's virtually impossible to tell you what they might be b/c they're so small. When looking from the side, do they look like a little anemone?

 

[utahsaltreefer]

Too hard to tell at this point. I hope its not 100 aiptasias 8O

 

[Manofathousandpolyps]

They are hydroids. I had some that matured into tiny jellyfish before they hopped off the glass and eventually got eaten.

 

[Anonymous]

I don't think there's any way to say for certain that they're hydroids. Lots of cnidarians have a juvenile polyp stage. It could be a jellyfish, for instance.

 

[Anonymous]

I have some of those on my glass too. When distrubed they look like a small fat short worm and just move somewhere else.

 

[Manofathousandpolyps]

Whoops, meant cnidarians not hydroids. EIther way, mine turned into tiny jellies.

 

[Anonymous]

Just in case anyone is interested, these are the differences between a cnidarian and hydroid...

The Phylum Cnidaria includes all animals with cnidocytes, the specialized stinging cell found in corals, anemones, jellyfish, etc. This phylum is divided into 4 classes:

Hydrozoa, which includes hydroids and the Hydra, common in HS biology classes, along with some hermatypic corals we call 'fire corals';

Anthozoa, which includes virtually all the corals we have in our aquariums, anemones, mushroom corals;

Scyphozoa, jellyfishes (but NOT 'comb jellies', which are in an entirely different phylum, Ctenophora);

and Cubozoa, which includes box jellies.

Cnidarians have different life stages that we call the medusa stage and the polyp stage. A polyp is something we're all familiar with, a medusa is basically an unattached cnidarian. When you see a picture of a jellyfish, it is almost always in the medusa stage. However, all cnidarians (as far as I know?) start life as a polyp.

What this means is that you could have virtually anything in there...

 

[silly34]

I find those on my tank quite often, I usuall just leave them alone or they get wiped off when I'm cleaning algea.

 

[Baianotang]

hydroids, what species well...?

 

[Mihai]

I also have lots of those. Nothing came out of them though :-(
They don't seem to mature in my tank.
M.

 

[utahsaltreefer]

For the most part they are now gone. There are still some around, but the majority have dissappeared. I did notice a small crab and a baby mantis shrimp pouncing on the larger amphipods though while I was watching!

 

[hdtran]

Matt,

Just so I get my set theory straight: All hydroids are cnidarians, but not all cnidarians are hydroids, right?

 

[Anonymous]

Correct.
I guess I didn't really make that clear in my post.

 

[hdtran]

Matt,

It was clear, but not blindingly clear (if I'm not mixing metaphors).

If I knew how to post it, I'd post either a Venn diagram, or that funny sideways U (belongs to) or the weird E (is included in the set of). But I'm getting way too geeky here...

Hy