Originally Posted by thekoimaiden
It could be a sign of high nutrients. You did say that your water changes lapsed. I have brown algae in my goldfish tank because the nitrates are around 30 ppm and a lack of plants. They're out right now due to a heavy salt treatment for stubborn fungus and fin rot.
I've always had a lot of algae, even when I was doing weekly 30% water changes! It's just that when I do a water change I usually clean away any algae that's started to grow on the glass, so I don't notice it as much I guess. I have quite a lot of plants, or rather, I mostly have this one massive Java Fern that just never stops growing. There are heaps of runners from it all over the tank, most of them much too big now to be considered runners anymore. I also have a cryptocoryne and a Lileopsis, but they aren't looking to great at the moment - not getting enough light because the java fern is smothering them I guess!
I know everyone will yell at me for this, but I don't even have a nitrate/nitrite test kit. Some time ago I bought some of the dip strip ones, which I know are meant to be really inaccurate, but I just couldn't afford the high quality ones! They're ridiculously expensive. Anyway, every time I tested the water, according to the dip strip there was 0 ammonia, nitrates or nitrites.
You'd think maybe after not changing the water for a while those waste products would build up alot, but generally what I notice when I don't change the water is the plants grow better and the water smells 'healthier' - you know, that 'mature tank' smell. Which I'm guessing means the number of beneficial bacteria is just increasing to match the bioload...