What is this? Should I be worried?

[Dr. X]

My 6 gal nano finished cycling a couple of weeks ago. The only thing I introduced recently was some cheato in a fuge. Today I find a bunch of these - on the glass, live rock, etc. The largest (pictured) is about 1/4 inch, or a bit less. They move like the entire front half of the thing is a mouth. Are they planaria? (I thought those were red/brown). Could some of my snails have reproduced? I have one large Trochus, three medium ceriths, three small nassarius and two moderate-sized margaritas. They do look like they are grazing on algae...

[strifilo]

Looks like it could be a flatworm. A parasite and not good to have.

[Elysia]

These are a type of flatworm, but they aren't what are known as planaria. These are copepod eaters. They aren't harmful, although I'm not overly fond of them. I use a small pipette and suck them out when I see them and when they are accessible. Otherwise, I ignore them. Their numbers wax and wane as the pod population does.

[Ohiomom]

Yep nothing to worry about..they will self limit in my experience..

[Frick-n-Frags]

it IS a flatworm. Whether those clear ones are pests is the mythinformation part.

the ORANGE FW's are definitely a pest for many people as they multiply like wildfire, then release toxinsd when they die "en masse".

btw: a parasite lives by sucking nutrients off of a host. just so you know what that term means.

that particular one in the pic does not do that. and neither do the orange ones.

[WharfRat]

Amphiscolops sp. are pretty harmless. Red ones can become a serious pest.

[Dr. X]

Thanks everyone. I just added a bunch of copeopods to the tank tonight, and it's at the office so I can't remove the ones I see. Oh well.

[MandM]

They are fascinating to watch on the glass. Nothing to worry about.

[HUNGER]

no there safe

[Elysia]

Originally Posted by Frick-n-Frags

it IS a flatworm. Whether those clear ones are pests is the mythinformation part.

the ORANGE FW's are definitely a pest for many people as they multiply like wildfire, then release toxinsd when they die "en masse".

btw: a parasite lives by sucking nutrients off of a host. just so you know what that term means.

that particular one in the pic does not do that. and neither do the orange ones.

HUH?

What was the "mythinformation" that you were clearing up in your post? We already determined that the animal in question is a type of flatworm. I know that some people find these organisms interesting to watch; I find them to be a mild "pest" in that they feed on a limited and valued resource: copepods.

Indeed, this flatworm is not parasitic. But the definition of that term has little to do with sucking; rather, the definition that concerns us here is: "an organism living in or on another living organism, obtaining from it part or all of its organic nutriment, and commonly exhibiting some degree of adaptive structural modification; such an organism that causes some degree of real damage to its host." {from Webster's third new international dictionary: of the English language unabridged with seven language dictionary. 1981.}

[leafeater]

Good information. I have never seen one of those but glad to know what it is in case it pops up in my tank.

[Dr. X]

I've been sucking up 5-10 of these a day off my glass for the past 2-3 weeks. They creep me out. I'm going to try Salifert Flatworm Exit. Not sure if it will work. I'll let you know.

[A sea K]

I had many of these in my tank while it was in its early stages. Their numbers would come and go for a while but eventually they all dissappeared never to be seen again.
I would not bother with treating the tank for what is IMO a harmless FW, the treatment in itself will likely do more harm than good.

[Juruense]

I also would do nothing about this non-issue.

Dumping crap in your tank is never the answer.