Flatworms with crazy eyes!

[reeferab]

Hi all - I’ve just noticed this little sucker on my glass. When I used the macro mode on my phone, saw that it had glowing eyes! Maybe it was just the angle of lights but super cool and weird.

Spotted another one on the glass without the glowing eyes.

Any ideas what they are? And if they are harmful to fish or corals?

 

[tbrown]

Looks like an Acoel flatworm.

Technically they're not harmful but they can multiply and start covering coral and causing irritation.

 

[ISpeakForTheSeas]

Waminoa flatworms:

Waminoa flatworms are photosynthetic (much like corals, they have symbiotic dinoflagellates living in them) and reportedly feed on coral mucus (not the corals themselves), so they tend to live on our corals - they're essentially harmless, but in mass numbers can basically smother the coral by blocking the light from getting to them.

Looks like it may be a Waminoa sp. - they are known to feed on the coral mucus rather than the coral itself of corals in the family Euphylliidae, as well as mushroom corals. Theoretically, in large numbers these guys could cause problems for corals like stated in the quote* below:
"Apparently, acoels can harm corals by smothering them, which may hinder their respiration, feeding and sediment shedding capacities."

*The link the quote was taken from:

Tissue loss in corals infested by acoelomorph flatworms (Waminoa sp.) - Coral Reefs

link.springer.com

Edit: Also, I have no idea why I didn't get the notification from Erin1971Texas' tag - sorry for the delay.

The only confirmed effective method of removal that I'm aware of is a repeated dip and cleaning method (pull any infected corals from the tank, dip them, scrape off any worms/eggs that stay on through the dip, repeat as needed). It may be more effective if you can to dip, scrape, and then put the corals in a different, uninfected tank to wait out the starvation of any eggs/worms in the infected tank, but this may not be possible. The link below has some other ideas you can explore if you'd prefer, but I have no idea if they're effective or not:

EEFW infestation (euphyllia eating flatworms)

Dip them using coral revive. They peel off in seconds using it. I’ve tried other stuff but nothing works even close as good as revive. They spaz right out in seconds and come off the torches Flatworm exit doesn’t work on these at all...

www.reef2reef.com

Edit: Also, here's a link that shows some more known host corals (I would assume these will host on just about any coral they can get too to be honest).

https://www.researchgate.net/figure/Photographs-of-Waminoa-specimens-and-their-hosts-a-Specimen-18-host-Echinophyllia-sp_fig2_324516348