Flatworm ID

[DEIGNAN14]

Noticed a few of these in my fuge today. I think they are probably harmless but would like to know what you think.

 

[DEIGNAN14]

Pic

 

[Greg Hiller]

There are a lot of species of flatworms. There are only two that I'd be fearful of. The big red ones, and those are usually pretty easy to spot. The Acropora eating ones, and I think you are unlikely to see those tooling around on the glass. The ones in the photo do not look problematic, but hard to tell from a photo sometimes.

Here's a pretty good photo of the big red ones:

How to eliminate Flatworms (Red Planaria) | Melev's Reef

Small reddish-rust colored creatures may already be in your tank. Or you may buy a coral and they'll appear as hitchhikers later. They may appear on the glass/acrylic, on the substrate, or on live rock. Due to their extremely thin bodies, they are called flatworms correctly. They appear almost...

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[FishieBusiness]

Red 1s bad, very bad. They are can easily overrun the tank if gone unchecked.