I agree with NM....I have a 55 at home that looks like a Chia Pet....all from less than 1 1/2 years. It is to the point that I have all but given up. Take the rock, snail and whatever else out & pull as much as possible.....then rinse before putting back in. If you try to pull under water, little strands will go through the columns and attach to other rocks. Run the Phos sponge too. What are your Phosphate levels? My mistake was using tap water for almost 6 years and not pulling it as soon as it started. The thing about this stuff is that you really cant see it growing until it looks like your front lawn.