I am confused into the posters reverences of Phosphate levels. Lets just clarify if we are talking about phosphate as orthophosphate (Po4)or Phosphate as Phosphorous (P-PO4)? I ask this because i stand to be corrected but the Hanna meter measures Po4 and not P-Po4 a PO4 of 0.36 is equivalent to a P-PO4 of 0.117. Hence my confusion.
Lets talk briefly about the Phosphorous Cycle. Natural sea water has an average P-PO4 level of 0.06 mg/l, but before you get all excited P-PO4 measured at reefs is often less than 0.015 mg/l. Probably due to the phosphorus uptake of the corals.
Phosphate enters our aquariums mainly by the foods we feed the fish. The fish digest the food and produce inorganic Phosphate. This Phosphate is then turned to organic Phosphate by mineralisation. There are many other processes that take place and influences such as DO and Ph but we will not discuss here.
So what does high P-PO4 do.
Phosphate "binds" to calcium and builds up in LR and substrate. This build up is a slow process and very difficult to remove once the level is high. One must note that we cannot measure (with our test kits) the amount of phosphate in the rocks and substrate. We only now that it leaches back into the water column with Ph fluctuations and water changes.
P-PO4 also interferes with the calcification processes of coral and coralline algae. This affects colour and growth.
P-PO4 also is fuel for filamentous green algae.
I have seen many a tank slowly deteriorate due to high P-PO4. IMO it is best to keep P-PO4 below 0.1 ath the very maximum. Best at P-PO4 0.013
