What is this and why is it so stubborn?

RussC · May 31, 2018

I've been trying to remedy this algae for some time now. Don't really seem to be making progress. The location in the back corners of my tank had me suspecting it was due to limited water flow there. Changed my power heads and increased flow. Now it seems to actually be growing. Literally removed it off the surface by sucking it out during a couple water changes. It came back. Its stubborn. Its getting a source of nutrients from somewhere. That's why I'm posting in this forum instead of general reefing. Thoughts?

Phosphates at 0.02. ALK about 8.4. CA about 420. I feed daily three-four small pieces of frozen food (total of a cube or cube and half) and some sinking pellets or flake food. I'd like to see this go away because its ugly. its not causing any problems and stays to my substrate only. And no other type of algae issues. In fact, I installed a UV light about a month ago and my brown algae on the back of my tank (which I never touched) is slowing going away. But not this.

What is it? Why is it different colors? Is that different types of algae? Thoughts? I have a couple of fish that don't eat pellets or flake so I do have to feed some frozen goodies.

Flippers4pups · May 31, 2018

RussC said:
I've been trying to remedy this algae for some time now. Don't really seem to be making progress. The location in the back corners of my tank had me suspecting it was due to limited water flow there. Changed my power heads and increased flow. Now it seems to actually be growing. Literally removed it off the surface by sucking it out during a couple water changes. It came back. Its stubborn. Its getting a source of nutrients from somewhere. That's why I'm posting in this forum instead of general reefing. Thoughts?

Phosphates at 0.02. ALK about 8.4. CA about 420. I feed daily three-four small pieces of frozen food (total of a cube or cube and half) and some sinking pellets or flake food. I'd like to see this go away because its ugly. its not causing any problems and stays to my substrate only. And no other type of algae issues. In fact, I installed a UV light about a month ago and my brown algae on the back of my tank (which I never touched) is slowing going away. But not this.

What is it? Why is it different colors? Is that different types of algae? Thoughts? I have a couple of fish that don't eat pellets or flake so I do have to feed some frozen goodies.

Your right about the flow. It's a combination of cyanobacteria and green algae. I would continue to vacuum it up during a water change.

Randy Holmes-Farley · Jun 1, 2018

I agree that it is at least partly cyanobacteria. There are tons of threads on it.

It usually grows best on sand, perhaps because it gets some nutrients from degrading detritus in the sand. But 0.02 ppm phosphate may not be low enough to be particularly limiting to it anyway.

Have you measured nitrate?

RussC · Jun 2, 2018

Okay, did some more water tests. Red Sea says Nitrates = 0. Hanna ULR phosphates checker still has me at 0.02 phosphates. That seems low. But, really, is it low as far as the hobby goes? Is there such a thing as zero phosphates?

Suspecting this is due to lack of flow in the areas, I've begun to really bump up tank flow in hopes of eliminating the detritus from settling in this area. I'm thinking I inadvertently created a fertilizer bed. Hopefully, I can remove what I see in each water change and the increase in water flow will help limit any detritus from settling in these two areas again.