Flatworms in Alpha

So...we have a bunch of tanks. A lot of them are small (we've been enjoying experimenting with tiny tanks, most in the 1 to 2 gallon range), and some of them are temporary (e.g. the clownfish fry tank), but the unofficial rule is that for any permanent tank that's 5 gallons or larger, we assign it a Greek letter. (We just started cycling Epsilon, which is a 29 gallon.)

Alpha has been around for a while. It's a Red Sea 20 gallon, and it's where Ozzie and Lara, our breeding pair of Darwin clowns, live along with a couple other fish and some of our favorite corals.

A recent picture of Alpha

Anyway, we've been having some trouble in Alpha lately. We had to frag that nice green Acro you see in the middle of the picture there, since bits of it kept mysteriously bleaching. Then one head of a lovely torch melted away in the course of a few hours. A montipora bleached. It's been kind of rough, and hard to pin down the issue.

This evening I saw one of these guys on the glass (it's not very big - just a couple millimeters).

Waminoa flatworm (aka pumpkin flatworm)

At first I was pleasantly surprised, because I thought it was a spot of coralline. Upon further examination with a handheld microscope, though, the, uh, eyespots down at the bottom of the picture do kind of jump out at one, don't they. (Also the tail.)

The good news is these aren't one of the REALLY bad flatworms, like the acropora eating kind. (I thought they were for a heart stopping few minutes.) But they probably aren't helping the situation in there.

I started reading up on them, and they are fascinating. They're full of dinoflagellates, for one thing -- they have these little symbiotic organisms that live inside them, almost like corals' zooxanthellae. For a while it was assumed that these were because they ate coral (and thus had the corals' dinos in their bellies), but that doesn't seem to be true for this particular type. (ref. https://onlinelibrary.wiley.com/doi/10.1111/j.1744-7410.2007.00082.x ) Instead, they pass these dinoflagellates down to their offspring, which is, I mean, wow.

Lookit all those dinoflagellates!

They do seem to eat coral mucus, which weakens the coral, and they also compete with the coral for tasty snacks in the water column, so they're not great. But they don't seem to directly predate on the coral, which is a pretty huge relief for us and for Alpha.

Here's a great paper on their relationship with coral: https://www.researchgate.net/publication/234705135_Epizoic_acoelomorph_flatworms_impair_zooplankton_feeding_by_the_scleractinian_coral_Galaxea_fascicularis

Anyway, as far as next steps -- we've been doing water changes and targeted dipping of specific corals, which we think should help, especially now that we know these flatworms are in play. We don't particularly want to dose the tank with any chemicals, so we'll keep an eye on things and see how it all goes. And, it looks like New Fish (a yellow banded possum wrasse whom we've had for a year -- we still haven't found a name that sticks, so I fear he will be New Fish forever) might be helping by snacking on these guys. Also Lara, who eats literally anything, including my fingers.

Hang in there, Alpha! I'd keep my fingers crossed if Lara hadn't eaten them.

(I'm joking about Lara, by the way. She nibbled at me once, but to be fair I was trying to steal her eggs at the time.)