po4 test - colorimeter

[Kip]

hi randy (or anyone else who can assist),

i, like most others, am constantly keeping an eye on po4. i have used habib's test and even at double resolution have gotten undetectable readings for po4.

so.. i took the next step and purchased a hanna colorimeter low range test for po4. ( as seen here ... http://www.hannainst.com/products/ion/photometers.cfm?ProdCode=HI%2093713 )

i ran the test and got 0.00ppm.

yeah, surprising. so i ran the test again. nada.

i ran the test on my tapwater and got the "over range" indication. (just wanted to make sure this thing picks up something)

so... I can conclude from this that i have 0ppm free po4.
but, that doesnt mean my system is po4-free... the po4 could be immediately biotically sequestered as fast as it is being produced.

right so far?

next question... NSW levels of po4 are around 0.07ppm. I assume that this has to be a free po4 reading as well. SO, does that mean that in any way my system could be nutrient (po4) deficient?

this is a sps system and i am chasing after better coral color. (some are noticably brown) hence, all of the po4 concern.

comments, suggestions, "your po4 is 0ppm kip, what are you worried about?" :)

thanks for your time,
Kip

[Randy Holmes-Farley]

It tests for orthophosphate (the inorganic form of phosphate in seawater), and I don't know that you can conclude from these tests alone that it is below any particular level, but I would conclude that it is adequately low.

It doesn't say anything about organic forms, but I do not think they are as important, nor generally worth testing for.

next question... NSW levels of po4 are around 0.07ppm.

Not surface seawater. It is usually much lower. Sometimes only 0.005 ppm.

Phosphorus: Algae’s Best Friend
http://www.advancedaquarist.com/issues/sept2002/chem.htm