Black brush algae..excess phosphates? - Excel
"Not enough light for healthy plants = algae.
Too much light and not enough CO2 for healthy plants = algae.
Too much CO2 and not enough light = dead fish and algae.
Wrong temperature = algae.
Improper any of the aforementioned for plants to utilize the available
macro nutrients = algae."
May I suggest the positive converse: keep your lighting low, grow
plants like Anubias, then you can have healthy fish and healthy
plants without worrying about CO2, fertilizers, temperature OR