My ATS have been up and running since 28 Dec. 2008, drop N and P to 0 in water column after 51 days later. So since 20 Feb. 09 I have been happy with the water testing results. Okay here is the problem, it's been 2 and 1/2 months since N and P at 0 level, but my hair algae is still growing like crazy in my display. The screen I have is 7 inches wide by 13 inches tall, actual area with growth is about 7 x 12.5, which should be more than enough for a 40G tank right? coz my math tells me that my ATS should be good enough for about 87 gallon worth. I am at a lost here. and i envy very much those of you that had reduction in hair algae growth in tank. Any pointers, wild guess, is much appreciated. Just for reference, here is the link of my ATS build viewtopic.php?f=2&t=88 and it's the same type of hair algae still. just more of it, all over rocks. scrubbed it all off in a separate bucket 2 weeks ago, but it's comes stronger and tougher now.