HELP! ID this algae, please.


New Member
Beginner reefer with a newish tank here. (about three months old) Can I please get an ID on this algae? Not sure what else it could be besides green hair algae, but I'm not very familiar with algae types yet.

This stuff is just completely taking over and showed up a week or so after my diatom booms receded. It's on the rocks, sand, overflow box, glass. My tank just looks awful right now. I'm running phosguard in a reactor and I'm going to get a few astrea snails tomorrow. Admittedly, I was overfeeding. I have cut way back on food recently.


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Snarky Shark

New Member
Cut your lights down. Recommend black out for 3-4 days. Looks like hair algae, maybe bryopsis as well.

Cut nutrients, light and remove as much manually as you can.

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Well-Known Member
Algae blooms are not unusual in new tanks. First, and very important, don't panic. Also, algae control is an ongoing process. It usually takes some time to see results.

Don't go out and use one of the various algae killer products. It's not that they don't work, but unless you correct the root cause of the problem, all you'll do is replace the problem algae with another algae that is much more difficult to control.

As for snails, think in terms of starting with about 1 snail per 2 gal of water, so if you have a 50 gal tank, consider about 25 snails to start with. I know this sounds like a lot, but you really need a decent number to make a dent in the algae. You can also consider hermit crabs or a mix of snails and crabs. Do not add these if you have fish that will attack them.

I have posted this before, but it's worth repeating here -

DaveK's Standard Lecture #2 - Algae Control

Algae control comes down to controlling nitrates and phosphates. If you have a problem with algae it is because these two nutrients are out of control. Do not think that just because your test kits read zero or low values that you do not have a problem. In many cases the algae is removing the nutrients and growing. This is why there is a problem.

Here are possible sources of nitrates and phosphates -

Feeding, especially flake food and not rinsing frozen foods before feeding.
Using tap water to mix salt. Always use RO/DI water for this.
"Dirt traps" and "nitrate factories" in the system.
Low quality carbon can leach nutrients.
Low quality salt can sometimes add nutrients. This is unusual today.
Livestock load on the system

Here are possible ways to remove nitrates and phosphates -

Water changes. Change 1/2 the water and you reduce the nutrients by 1/2.
Skimming. Remove the waste products before the biological filtration need to break then down.
Nitrate and phosphate removal products.
Deep sand beds.
Algae Scrubbers.

Each of these has advantages and disadvantages. Most people that control algae will use many of the above methods.

There are also other items that can effect algae growth rates.

Good clean up crew.
Other livestock that eats algae.
Low general water quality, especially when the readings are off.
Lighting, sometimes you can reduce it, especially in FO or FOWLR systems.
Old light bulbs. Colors change as they age and this can be a factor.
Water flow. More flow will often help keep algae down.
Manual removal. Very important, especially when there is a big problem.