Green Hair Algea


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May 8, 2021
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New Zealand
Okay, there's a million posts and youtube videos on this topic but I'm at a loss here. Feels like I've read them all, watched them all and tried almost everything. Nothing is working.

Here's my set up. 120-140L system with sump, Hydra 26 light on for 6 hours, 3 clowns, royaldotty and a yellow fin damsel. All happy and 3 years old. A mix of soft and LPS coral. I do a 10L weekly water change, always Fri/Sat and add Vibrant etc after. I'm using RODI filtered water.

I've tried 4ml of Vibrant weekly.
ROWA phos in a bag in sump
Aqua Forrest Phosphate minus in reactor (100g replaced every so often)
2ml of Hydrogen peroxide daily for a week
Lights out for 3-4 days
Reef RX

I recently got new filter socks, took a while to come from China. Was using an old one which was just holding together. Put a new one on, left it for a week and it's still very clean.

My questions really are

- What mostly causes it? (Nitrates, Nitrites, Phosphate or light?)
- How can I tell which one is the issue, all my tests come up normal levels (but likely because the GHA is using it up therefore not showing on tests)
- Is Aqua Forrest Phosphate Minus or ROWA Phos better to use to remove phosphate in a reactor
- What's the most recommended method? (it's mostly short to hard to remove by hand)
- Aqua Forest - how much should I use and how often should I replace if I do this?
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No, it wasn’t expensive dear....
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Feb 21, 2017
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Nottinghamshire England
GHA generally uses phosphate as a food source and can give low test readings because of this .

I use rowaphos 24/7 but you really need it in a reactor in a tank that size for it to work correctly. It won’t be very effective in a media bag with the water volume you have.

You also need to change it frequently to start with as phosphate may leach out from your rockwork as the levels in the water drop. If you don’t change it, it won’t work properly


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Oct 17, 2015
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Garden Grove
I feel your pain. I've been in a heck of a battle for a few months now. I also test zero but I know that's due to uptake.

If i run GFO i feel like my sps struggle a bit so I've been avoiding it.
I've had best luck with manual removal. This includes a small pair of angled hemostats, that lock when you clip them. cheap on amazon if thats available to you. I basically clip a section and spin it up like spaghetti then remove into a bowl of tank water. Once I get it short I'll brush it. You can find grout/cleaning brushes of all shapes and sizes pretty cheap. From there I've found a good clean up crew helps keep it back but I have to get it there. My hardest workers are:
Tomini Tang
Lawnmower blenny (MVP)
Seahare (keep a close eye if you go this route, if they die they can cause more harm to the tank)

Those are the only ones I see actively consuming GHA. The big BUT is I have to get it clipped way low if not off or they'll just work around it in my experience. My display is 75g or about 280L. I added a huge amount of snails and hermits and I'm sure they help but didn't do enough for me. If you can source a lawnmower blenny that could be a game changer in your size system. Any rock work you can manually remove and scrub in a bucket during a water change will help tremendously. Mostly form paranoia I run carbon if I plan to scrub algae in the tank.

I got GHA by feeding heavy for anthias but also from silicates in my RODI. My meter was reading zero but when I sent in a water sample to ATI they tested my RODI as having silicates present. Just something to keep in mind, I swap DI at zero and actually run DI followed by a silicabuster cartridge from spectrapure now. If you suspect maybe your filters needing replacing or you TDS is registering at all swap them to be safe. Clean your barrels/buckets and inspect your mixing pump.

It's been a heck of a lot of work but I'm finally getting the better hand.

I'll say I wasted a lot of time trying to manipulate things without physically getting in the tank. Now, I strongly feel with GHA you gotta get in there and stay on it manually until coral or you cuc get the better hand.


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Feb 12, 2017
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San Angelo Texas
+1 on the manual removal. Especially the removing rocks and scrubbing them in a bucket during water changes. I got a couple of urchins to help keep the scrubbed rock clean and they worked very well.


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Dec 31, 2018
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San Diego
I went through a crazy gha breakout for my first tank that I don't think I truly ever got under control. For my second tank, I also went through a gha phase but what helped was manual removal, followed by filtration through a filter sock back into the sump so it didn't spread everywhere, vibrant, and turbo snails.

About a month of that and it finally went away. Throughout, I fed normally and did regular water changes.
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