Need Some ID Help - Bryopsis or GHA?

[hendo50]

Hi All - I'm still pretty new to reefing, was having really good success for about a year, but the last 6 months have been an endless slog through a gnarly algae outbreak, to the point I'm getting disillusioned with the whole thing. My nutrient levels have all been g

I have a 33 gallon Fluval Flex, and it's been running now for about 1.5 years. Bio load is fairly small (1 clown, 1 midas blenny, 1 orchid dottyback, 1 blue/green chromis), with minimal coral (just two smallish, but very healthy Zoa colonies) and my nutrient levels were pretty stable for about the first year (NO3: 5-7.5, PO4: 0.02-0.05).

The issue started ~6 months ago when I started showing a little (what I thought was) GHA and cyano, but was small enough I just sucked it out and moved on.

It eventually grew to a big enough problem that I decided to really go at it. So last May I tried Dr. Tim's 2 week Waste Away and Refresh treatment, followed by a 3 day blackout. That caused my NO3 levels to drop to zero (PO4 stayed pretty level), and what was an annoying problem exploded to a complete tank takeover.

Since then, I've tried just about everything I could think of shy of nuking the tank: increased flow, changed feeding, syphoned areas I thought were nutrient sinks, blackouts. I even took down my aquascape, vacuumed the whole sand bed, scrubbed the rocks, put them back in and did a 3 day blackout. No luck.

Now this stuff is everywhere and I'm at my wits end. Neither my hermits, astrea snails nor nerite snails seem to touch it, in fact now they stay off the rocks almost entirely. So I started thinking bryopsis - but it doesn't look quite right, still I tried a Flux regimen, which of course didn't touch it.

Any help figuring out what this crap is and what I can do about it would be greatly appreciated!

 

[blaxsun]

It looks like mostly GHA.