Observed vs Actual Phosphate

[Mules1]

I apologize in advance if this has been asked before.

If the observed PO4 in the tank is 0.03 which is what we all strive to reach but we know that the level is actually much higher because of visible algae in tank and sump that are consuming it are the coral still happy?

In other words are we trying to achieve an observed or an actual level of 0.03 phosphate or lower.

[tmz]

Actual is what we are concerned with but ther is no way to measure that wit hany precison . Tests only tell you how much inorganic phosaphte ( PO4 species) are in the water sample not the phospahte bound to organics or surfaces . Making it harder is the fact that most tests have a range of accuracy of +/-.04ppm. Then there is potential leaching from the rock or substrate and variable levels of organic phosphate. Keeping PO4 in the water below .03ppm over time usually leads to less overall overtime as some algae wanes and leaching from the substrate and rock equilibriates. Further depleting Po4 too low too fast can stress some organisms.

[bertoni]

There are lots of nutrients in our system, and many forms of phosphorus. Keeping the measured phosphate under something like 0.03 ppm can help with many problems, but other nutrients can cause problems, too.

I'm not sure what you mean by the actual level of phosphate. Our kits measure only orthophosphate, which is the prevalent form of dissolved phosphate in our systems.

[GroktheCube]

Does the Hanna ULR Phosphorous meter measure other forms of P beyond PO4?

[bertoni]

No, it measures only orthophosphate. Hach sells a total phosphorus test kit, but I think it's somewhat complicated and time-consuming, from what I can tell.