Emerald algae on my hornwort, bad?

[E Blue]

Is this bright emerald stuff bad?

[Crabby]

That looks like blue-green algae, Cyanobacteria. It does quite quickly all across your aquarium and is extremely hard to get out. I recommend taking that piece of hornwort out (or at least trimming that part off), and maybe looking into how to get rid of it if it does start spreading more.

[jayc]

Yep, cyanobacteria like Crabby said.

Get rid of it as quickly as possible.

[E Blue]

Ok cut that spot out and another chunk that had a couple suspect areas of a greener cast. Eyes peeled for any others showing up. How have I developed Cyanobacteria? Too much BacteAE?

[Crabby]

Probably not the BacterAE. Cyanobacteria is usually caused by a combination of low flow, excess light, and some sort of nutrient imbalance. I believe phosphate is quite tied into it (too high or too low can cause a bunch of different algaes), and of course high levels of nitrate (waste) will lead to algae outbreaks. Chances are you'll get some more showing up, so maybe drop light levels and test nitrate?

Edited March 7, 2021 by Crabby

[jayc]

Low water flow or in other words, low oxygen levels in the water.

Does your tank have any filter outlet breaking water surface tension?

[E Blue]

I cleared out 50% of floating plants. HAng on back filter moves surface and water below pretty well. I can cut back on light hours. Not much other algae around the tank. Just checked nitrates via sapi tested 0ppm.