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View Full Version : Nitrates = 0 phosphates = 0


buddah001
06/28/2017, 11:10 AM
Just got my Salifert test kits for Nitrates and Phosphates from BRS last night and they both =0???? I have some sort of nuisance algae going on but how could this be? I can't see this stuff sucking everything out of the water.
Ammonia and nitrites are 0 also....
You do want some of both correct.

Dan_P
06/28/2017, 03:09 PM
Just got my Salifert test kits for Nitrates and Phosphates from BRS last night and they both =0???? I have some sort of nuisance algae going on but how could this be? I can't see this stuff sucking everything out of the water.
Ammonia and nitrites are 0 also....
You do want some of both correct.

Things to consider.

Test kits have a lower limit of detection that is greater than zero. So in sense all kits are a bit dishonest about their abilities to indicate low levels of analyte.

Nuisance algae will grow quite well with nitrate and phosphate at concentrations that tests cannot detect.

So, there is no need to invoke nutrient release from rocks or nutrient absorption by the algae when you observe algae growth but measure no nitrate or phosphate.

Horace
06/29/2017, 02:00 PM
I will say that while you may see 0 phosphate, you likely have more than enough. If you are testing 0 nitrate, that is probably not a great thing. Most tanks with 0 on salifert tend to look poor. Softies REALLY dont like water that clean, and in many cases cant even survive. In my tank that was low nutrient, Xenia lived about 1 week, then shrivled up and died. SPS colors also fade dramatically, with the most notable being Greens. Greens fade to non-existent and reds turn to pink etc. Growth also grinds to a halt.

chevegan
06/30/2017, 09:04 AM
easy answer (occam's razor) the algae is keeping your nitrates and phosphates at zero. They are in effect your algae scrubber :)

tmz
06/30/2017, 11:24 AM
Some algae is oligotrophic(can thrive low inorganic nutrients). Zero readings for N and P may be more than true zero. IME, NO3 near zero ,barely detectable with a salifert kit ( say 0.2ppm to 1ppm) with PO4 around ).02 to 0.04ppm is sufficient to minimize many nuisance algae issues and good growth for desireable organisms like corals.

It is also possible that some PO4 is leaching from live rock and/or sand and being used by some nuisance algae.

"Occams razor" pushes for the simplest most parsimonious hypothesis which may be a good first reach but often does not fit given the myriad of variables involved in a reef tank.

Dan_P
06/30/2017, 01:24 PM
The Occam's Razor in this case sounds good but is not likely to supported by science. I will go out on a limb and say there is never enough nuissance algae growth to keep phosphates and nitrates undetectable. The reason is one of insufficient biomass accumulation and therefore insufficient assimilation of nutrients to keep nutrient levels below detection limits. Algae does store phosphate in excess of what it needs for generating biomass but this is still not enough to invoke the "algae is soaking up the nutrients and masking a nutrient problem"conjecture.

Macro algae is around 80% water. Nitrogen makes up about 5% of the dry mass, phosphate around 0.1%. An aquarium covered in hair algae would not have much algae biomass to mask a nutrient issue.

The story is more complicated.

tmz
06/30/2017, 11:58 PM
How old is the tank,btw? I'd also check for detritus accumulations and siphon them out