Stubborn GHA

[Deriak4942]

Hello everyone! Long time stalker...hoping to become active member.

So my setup in about 3 years old and about a month ago I had less than perfect water parameters. I have since got my water quality where I want it but I still have some stubborn GHA that won's go away.

System:
20g display
5g hang on refugium with nano skimmer and chaeto
1 small hang on with chemipure
quad ho t5 lighting (2 actinic, 1 10k and 1 Pink)
2 koralia nano circulation pumps
1 Jebao wave maker
Phosphate reactor with GFO

Water parameters:
Salinity 1.024
Nitrates: 0
Phosphates: 0-0.03
Alkalinity: 9
Calcium: 450-500
pH: 8.3

Live stock:
Many corals sps & lps
1 clown
1 cleaner shrimp CUC

I'm most concerned with the GHA on my acropora. It took a tumble a little over a month ago when my water wasn't perfect and GHA showed up in the damaged areas. Any input would be greatly appreciated. I've been considering a blackout...

 

[ange062]

I've found that running Phosban in a reactor is the most effective (have experimented with probably a dozen different types of phosphate reducers). Raising Mg levels to 1500-1550 also helps with algae. A turkey baster and toothbrush are the best ways to manually remove and keep things clean of detritus.

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[Deriak4942]

I've tried to remove it from the acropora with a toothbrush. It's quite locked in there...I can't brush away the base.

I didn't know magnesium played a factor in algae. I haven't tested for it in 3 years...

 

[Deriak4942]

I've ordered a salifert mg kit...

Are manual removal and blackout my only options?

My phosphate tested 0.03 3 days ago and 0 yesterday and today. I've manually removed all I can and that's what's left. What remains doesn't appear to have grown over the last month.

 

[ange062]

I wouldn't do a blackout since you have corals. Go with manual removal and phosphate reduction (phosban, raise Mg, weekly water changes, etc). And be patient, it'll probably take a month or two of diligence to get it all knocked out.

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[Razorback reef]

If I remember correctly bryopsis likes phosphate. Hair algae feeds mostly on nitrates.

Reduce feeding, add activated charcoal, and increase water changes.