Unknown Critter

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Ben K

Aquarium Advice Activist
Joined
Nov 15, 2006
Messages
101
Location
Ontario, Canada
Hello. I just bought some fish today to put in my tank to replace some fish that died on me. But I noticed a few critters in my tank.

The first one is a small white speck that seemed to be swimming around. I am pretty sure this is ich, so I dosed my aquarium with Ich treatment and increased the temp.


The second one I am unsure of. At first I thought it was a shelless snail, as I do have a snail problem I am battling. But upon closer inspection I am doubting this. These things range in size from 1mm wide and 5mm long to 1.5mm wide and 10mm long and have a spade like head. They are very thin and are a off-white tan color like this:
colordab.jpg
(the dab in the center of the image)

I went and tried to kill one, cutting it into half with a sharp pocket knife. The back half remained dead while the half with the head moved about still.


As I watch this, I noticed another, so I cut it into four. Same thing, the head part is still moving. I have seen several of these things. They seem to be crawling around the gravel like a snail.

Any idea what they are or if they are harmless or dangerous to my fish?
 
I'm certain that's planaria, a somewhat common (and harmless) worm in the aquarium hobby. If you start noticing them, especially in large numbers, it's usually a sign of overfeeding or too much food accumulating in the gravel.

Edit: Oh, and in a rather strange twist, your cutting actually replicated a pretty common high school biology experiment/demonstration. They're much like a starfish in that they can regenerate from small pieces (except the starfish requires a piece of the central disc, planaria don't require anything). When you cut it, each piece of planaria, unless it's squashed, can grow a head and function as a new worm. With careful incisions you can even make planaria with multiple heads on one body
 
Well...strange turn of events, I've somehow killed off all these critters plus all of my snails without harming the fish....even though I don't know how.
 
planaria. I wish I had some in my tank. Great natural fish food source.

If you want them dead, drop a penny in your tank overnight. the copper will leach out and kill them (and any snails, possibly any shrimp too). Then do a water change.
 
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