Which hair algae, and what to do about it?

[jccaclimber]

TLDR: What is it, what do I do about it?

Full version:
First I had a tank taken over by 95% bryopsis and 5% hair. Fluconazole took care of the bryopsis, thread here:
https://www.reef2reef.com/threads/confirm-id-bryopsis.440272/

Unfortunately waiting several additional weeks for the fluconazole to take out the hair algae resulted in the hair algae taking over instead. At the same time, my chaeto is back to not growing well, my grape caulerpa is doing decently, my feather caulerpa died out, and whatever other caulerpa I had (looked like smooth blades of grass 3/8" wide by 4" long) has also died out. At this point the (undersized) skimmer has its cup back on and has been chugging away for a few weeks.

The coral is all doing great, but I'm losing sight of my rocks.

I did throw in a sea hare (dolabella) recently, although I'm not sure he's doing anywhere near enough. Being a 600 gallon system I doubt a single sea hare is going to do the trick, so I'd rather identify and cure my imbalance whatever it may be.

It's brown/dark green to my eye, more green when I take it out of the tank. It is only slightly slimy. Sometimes it tears off of the rocks ok, other times I end up picking up the rock by a tuft of algae. It gets a 2-4 inches long. There is also some cyano, but not a ton.

Nitrates (Red Sea Pro) are between 0.25 and 5 depending on how frequently I've dosed (it grows much faster when I do), phosphates per Hanna ULR are ~0.04 at last check, but obviously being consumed by the algae growth.

Bare slide:



Microscope pictures (40x, 100x, 400x):




Another at 40x:


And once more 40x, 100x, 400x. I could get pictures at 1000x, but DoF is poor and I'm not sure they'll say much.

 

[jccaclimber]

As an additional note, it is fairly responsive to H2O2 out of the tank (what isn't), but not particularly responsive to H2O2 in the tank, even pumps off. The rest of the tank gets unhappy, and the algae doesn't seem to mind much. I've used H2O2 with success on other algae in the past (generally on smaller tanks), but it isn't working out well in this case.

 

[1979fishgeek]

Did you ever resolve this algae? Looks remarkably like the stuff I am battling, nothing eats it and I’ve driven ny Nitrates and phosphates to undetectable in attempt to starve it off, but it’s still thriving and now my sps are getting pale. Driving me nuts!

 

[jccaclimber]

Nope. My coral is happy, and growing nicely, but the algae is doing even better.

 

[1979fishgeek]

I spent the day syphoning it off the back glass, it came away very easily. Hoping now it’s only in a few places that one of my Tangs or lawnmower Blenny might eat the rest. I don’t like using chemicals but if this dont work I will have to try Fluconazole.

 

[jccaclimber]

If it's only in one or two places I would turn off all of your pumps, suck out as much as you can, and do a heavy H2O2 spot treatment for a couple days to see if you can eradicate it.

 

[1979fishgeek]

If it's only in one or two places I would turn off all of your pumps, suck out as much as you can, and do a heavy H2O2 spot treatment for a couple days to see if you can eradicate it.

I syphoned it out Monday, it never even needed scraping it practically fell of the glass with the syphon. I, hoping that’s a sign the ulns was having a effect on it after all. My sps had gone pale and my zoa were shrinking from the extreme lack of nutrients, I was shocked the algae was still there. I’ve back off the carbon dosing and noticed the fish and clean up crew now pecking at the glass where it was.

I’ve never done H2O2 treatment, I will start researching it just encase! Thanks for your help.