What kind of algae is this?

[Byron]

I’ve never seen this before in my tanks and it just started growing in my planted 55 gallon tank. It’s not spreading at an overly alarming rate but it’s still really gross. Looks like a plasma or slime. It’s only on the sand.

Cyanobacteria is caused by organics in the presence of light. The only way to effectively deal with it is to reduce the organics. I also see a lot of troublesome algae on the rocks and plants, also organics are to blame. The light may or may not be too bright, it is the organics that you must reduce.

Substantive water changes, filter cleanings, less fish food, no plant additives for the present--these will help with the organic load. Overstocking the tank cold also be a factor if applicable, not saying it is as I don't know the fish load/volume etc. Blackouts temporarily resolve this but it will only return if the organics that feed it are not eliminated.

BTW, a white substrate aids this because it reflects light. Aside from its other issues for the fish.