I think Brown Hair Algae (Help identify !)

[Delly]

Hello everyone,

My tank has been up and running with saltwater in it since July 2026, but has only had fish in it since August 2026.

I started to get what I think is brown hair algae which I here is really comon to new tanks.

I have dry rock, and 20lb of Caribsea live sand, as well as 8lb of ULS from TBS. I also have 5lb of rubble rom TBS.

The sand and rubble have been in the tank for about 3 months I would say give or take a week or two.

I just started to turn the sand with the dry sand that is sitting underneth.

Do we all think this is Hair algae? If so any fish or CUC I should Look into?

Thank you for reading,
Delly

 

[Tinnerito]

Hello everyone,

My tank has been up and running with saltwater in it since July 2026, but has only had fish in it since August 2026.

I started to get what I think is brown hair algae which I here is really comon to new tanks.

I have dry rock, and 20lb of Caribsea live sand, as well as 8lb of ULS from TBS. I also have 5lb of rubble rom TBS.

The sand and rubble have been in the tank for about 3 months I would say give or take a week or two.

I just started to turn the sand with the dry sand that is sitting underneth.

Do we all think this is Hair algae? If so any fish or CUC I should Look into?

Thank you for reading,
Delly

That's really early to have that much hair algae, but it shouldn't be a big deal as long as you maintain it. What are your nitrates and phosphates looking like? Not just the numbers themselves but staying in a 100 to 1 ppm ratio between the two is a good practice to sustain balance.
Focus on the nutrient balance first. Once everything looks good it's probably a matter of gradually adding herbivores, but every tank is different.

 

[Delly]

To be 100% tuneful I test just about every week and I have been been able to really get a good number for my Phosphates and Nirates they are all 0 when I test them. I have been using Salifert tests and I just cant get anything to be over 0. Everything looks clear to me.

Delly

 

[EnterName]

A microscope would help, but sometimes diatoms attach to green hair algae and make it look brown. The blue light can also change the perceived color, try white lights

I'm sure a CUC and sufficient water flow will fix the issue. Within the first few months (if not the first year depending on the setup) tanks do all sorts of weird things.

 

[Tinnerito]

To be 100% tuneful I test just about every week and I have been been able to really get a good number for my Phosphates and Nirates they are all 0 when I test them. I have been using Salifert tests and I just cant get anything to be over 0. Everything looks clear to me.

Delly

0 Nitrates and 0 Phosphates still signals nuisance algae. It's about the balance, not the number. Organisms like coral and macroalgae benefit from certain nutrient concentrations but if nutrients go out of balance, or say they're at 0; that's when nuisance algae takes advantage of the sterile environment and takes over. Especially IME, most cases I got nuisance algae because my macroalgaes depleted my nutrients to 0.

As EnterName suggested, it may also just be diatoms which are completely normal in young systems, and should clear up after some time.

 

[Delly]

0 Nitrates and 0 Phosphates still signals nuisance algae. It's about the balance, not the number. Organisms like coral and macroalgae benefit from certain nutrient concentrations but if nutrients go out of balance, or say they're at 0; that's when nuisance algae takes advantage of the sterile environment and takes over. Especially IME, most cases I got nuisance algae because my macroalgaes depleted my nutrients to 0.

As EnterName suggested, it may also just be diatoms which are completely normal in young systems, and should clear up after some time.

hmm interesting what is IME?

 

[Delly]

A microscope would help, but sometimes diatoms attach to green hair algae and make it look brown. The blue light can also change the perceived color, try white lights

I'm sure a CUC and sufficient water flow will fix the issue. Within the first few months (if not the first year depending on the setup) tanks do all sorts of weird things.

Maybe something like a CUC and a Lawnmower Blenny?

Delly

 

[Delly]

I also do a water change about every 15 days, and around 13-14%. of the water.

 

[Tinnerito]

hmm interesting what is IME?

IME=I'm my experience. For sure look at the algae though under some white light. It does look kind of like ordinary diatoms but it's hard to tell in the picture

 

[EnterName]

Maybe something like a CUC and a Lawnmower Blenny?

Delly

It will depend on what it is. Note that it's not unlikely the algae growth will vanish and then neither CUC nor Blenny have something to eat (besides what you feed). So make sure everyone (including the CUC) is cared for. They very often starve in tanks, especially young ones because once the main algae issue is cared for not enough biofilm is growing.

 

[Tinnerito]

Maybe something like a CUC and a Lawnmower Blenny?

Delly

Most CUC are not obligate herbivores, so you'd have to get something that specifically eats algae. If you confirm it is hair algae, I would start with something like a colony of Trochus or collonista snails. Lawnmower blennies are great too, but they tend to only eat fresh, incoming algae rather than long established hairs as for their scraper like jaws. My banded trochus snails do a great job at eating algae though. They eat all day, can flip themselves back over, and clear up algae real fast. As EnterName said, it is good to consider the possibility of algae depleting, so having dedicated nori on standby is good for the event that your herbivores run out of food.

 

[Delly]

I took a video , on one of my trochus snails, and a still as well. Does this help depict what it might be? I don't have a microscope atm.

It is a little long and stringy when it flows.

 

[EnterName]

I took a video , on one of my trochus snails, and a still as well. Does this help depict what it might be? I don't have a microscope atm.

It is a little long and stringy when it flows.

Looks like "normal" green hair algae to me. Something like Derbesia spp. pretty normal stuff.

 

[Delly]

Now people say green hair algea, but this looks brown to me is that just because of the light? Also thank you for looking at the video .

Delly

 

[EnterName]

Now people say green hair algea, but this looks brown to me is that just because of the light? Also thank you for looking at the video .

Delly

The filaments are very thin and "green" is a spectrum
Depending on species and nutrient/trace element availability and light, color can differ quite significantly. Here are two green algae species up close:

The left one looked quite "brown-ish" with the naked eye as well.

Actual brown algae is relatively "rare" in reef tanks in contrast to green and red algae.

 

[Delly]

The filaments are very thin and "green" is a spectrum
Depending on species and nutrient/trace element availability and light, color can differ quite significantly. Here are two green algae species up close:

The left one looked quite "brown-ish" with the naked eye as well.

Actual brown algae is relatively "rare" in reef tanks in contrast to green and red algae.

ohh lovely, I can't wait one day to get myself a microscope and see this for real. Then I will be a true reef nerd !!

Thank you so much for the help,

Now I will research how to mange this.

Delly