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New unidentified critters in my reef tank


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These little guys showed in my reef the last two days. Can anyone identify them' date=' and are they harmless?[/quote']



I'm about as far away from expert as you can imagine, but I think I've seen this listed as flatworms on many sites. From what I know, some wrasses can keep them in check, or you might have to take a chemical approach with flatworm exit (and a siphon). Can someone more versed in these things help out?

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Indeed those are flatworms. You will want to make sure and keep those guys under control. They will end up reproducing quite rapidly as you already probably know. That variety doesn't really eat any of your corals, but they are unhealthy for them. What ends up happening is that they flatworms will flatten their bodies out over a coral and suck in as much light from above as they can. They kindof use the coral as protection and end up hogging alot of the corals light needed for photosynthesis by the corals own zoanthilia. The corals will sometimes end up shrinking or just not fully expanding. Sometimes it just slows growth in the coral.

Unfortunately they are not the easiest little buggers to get rid of. I have seen six line wrasses eat away at them as well as arrow crabs. There are a few others out there that can help with that too. Flatworm exit is a good tool, but you will have to be very careful with it. Do some reading up on this on some of the forum pages and see what others have to say.




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I had them and use Salfert Flatworm eXit. I was scared by others and that the flatworms can release a toxin when they die. So I spent about two weeks with a small siphon (air line hose) each day sucking as many of them as I could out of the tank.


When I got the population down to almost undetectable levels (only 5-10 visible on the glass at a time) I used the flatworm eXit. Follow the directions and you should have no problem. Make sure you have a big canister of carbon to add once the flatworms start to die (about 30-45 minutes) to remove the toxin that they release.


Good luck. Many people here have had these as a pest and survived. I would rater have flatworms than the monti-eating-nudibranch that I have had recently. Flatworms are a lot easier to get rid of IMO.



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