I believe GHA is related more to P04 than N03. I recently (summer) combined 2 tanks into one sump. One of the tanks had high P04 (over 1.0) and now my other "clean" tank has started to show some GHA. I run both biopellets (for several years) and GFO, but my while my N03 stayed at zero, my P04 is still around 0.10 (although dropping now) with the combined tanks.
I have beat GHA before by running GFO, and it took a while at zero P04 before it finally let go. So it seems that it does not take a lot of P04 to get GHA happening.
Good news with my tank, is that GHA is now starting to subside again, which seems to be coinciding with my P04 dropping. I just need to keep doing my weekly toothbrush routine on the rocks, to be sure detritus doesn't get trapped and feed the GHA.
The ironic thing, though, is that my other previously high P04 tank has no GHA problem, despite having less internal flow and live rock that was saturated with P04 (presumably). So I can't say that I totally understand what causes or mostly fuels GHA. It could also be because of the foxface and kole tang I have in there. However, I do have a yellow tang in the tank where I do the problem, and he does spend all day picking at algae (lots of green poop, too,...LOL).
Last edited by Reef Pilot; 10-10-2013 at 03:00 PM.
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