I think I have green spot algae on the sides of my tank (but not the plants). Is this that?
The tank is 120 gallons, no tech. Three large goldfish and jungle vals in sand. It's been stable for about 4 years but this started to crop up several months ago. Indirect sunlight plus 2 36" Current Nova SLR T5s which are down to about 1 bulb (can't tell what it is). The algae started before I lost so many bulbs though. Tank is unheated, undosed, unCO2ed, and pretty much neglected. Fish and plants are healthy, as is the spot algae. No other algae except for a little fuzz on a branch.
Do I need to add phosphate or will a heavy water change suffice? I have a test kit somewhere which is probably expired...I've really slacked on this stuff and as long as things look okay and the animals are healthy I've been letting them be.
So is it green spot? It's very dark, almost black. And it's a real %&*)$* to remove. Thanks!