04-13-2012, 10:29 AM
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I suspect we are talking about three different "problems" here, and each may have its own cause/solution.
The easy one is the green dot algae (as it is commonly called) that appears on the glass. This is light-related, though other factors are likely involved. It is easily dealt with. Scrape it off during the water change. To keep it from coming back, clean the inside glass at each water change with one of those sponge-type scrapers. I always run this over the inside front glass, and periodically the other sides, whether I see anything or not. Not doing it for one week invariably means that before next week a dot or two will appear. This weekly clean catches it before you see it. And once you see it, it can be stubborn to remove, requiring a hard scraper and sometimes even a razor blade (careful not to scratch the glass).
The green "algae" ion the substrate may be cyanobacteria. A photo would help. If this is what it is, a green slime that easily rubs off, it is caused by organics. Light is obviously needed, but organics cause it. I have seen it suddenly appear when the filter has not been cleaned, then disappear as soon as the filter is cleaned. Excess organics in the tank can come from overfeeding, fish waste, insufficient water changes, insufficient filter cleaning, and lack of substrate vacuuming [in planted tanks this is a bit different].
The brown string I am not sure of, a photo would help here too. This sounds like something I've experienced, it is not algae but organics. I have only seen it in tanks that also had cyano at the same time, so I suspect the same causes/solution.