[ChrisKirkland]

Originally Posted by CUNAReefer

Some interesting reading on algae and low phosphates. I received this from Christopher Brightwell a couple of days ago...

"The Biofilm
One of the complaints often voiced by some aquarists using this method is that a
short, brownish film forms on static surfaces (as previously mentioned, it is most
prominent on aquarium panes and less so on live rock and sand) that detracts from
the overall appearance of what would otherwise be a “pristine” display. Ironically, the
film seems to be directly related to insufficient phosphate being present in the system.
The current theory, based on research recently presented in Nature, is that
cyanobacteria in phosphate-limited ecosystems can shift from the utilization of
phosphorus to sulfur and/or nitrogen compounds in their cellular tissue. Of greater
importance, in our opinion, is that in many cases the appearance of brown
cyanobacteria is an indication that the phosphate concentration in the system is too
low for long-term survival of corals. The experiences conveyed to us by many
aquarists indicate that corals maintained in these conditions appear to be more
susceptible to succumbing to infections or suboptimal conditions that would normally
© 2010 Brightwell Aquatics. All rights reserved.
not be considered lethal. This is, perhaps, what is meant by some experienced
aquarists as “maintaining the corals on the knife’s edge between life and death”.
Rapid- or slow-tissue necrosis and/or bleaching may result if the situation is not
remedied, which may be achieved by increasing dosing rates of CoralAmino,
Vitamarin-C, and/or Restor, and/or by decreasing the dosing rates of MicroBacter7,
Reef BioFuel, and the utilization of NeoZeo media in the system. Encouraging water
flow within the main aquarium and regularly cleaning these surfaces tends to
decrease the propensity for biofilm formation inside the display. Additionally, several
species of Acanthurids will graze on this film, helping control it and simultaneously
recycling some of the constituent nutrients (which decreases the need to feed)."

Hope this helps you as I have suffered from the same issues described in this thread. Maintaining some phosphate in my system has helped quite a bit.

Warmest Regards,
James

Very interesting read, I always knew it was a balancing act between the correct amount of PO4 and not having too much or too little.