ATI Test Results

[RockyProndoa]

So I finally received my results back, and I am a bit concerned about some of the values - first being salinity. Test reported it at 30.21 PSU, my Apex and refractometer both test around 35-36.

Second issue - phosphorus vs phosphate. Phosphorus tested at 5.99 micrograms, while phosphate tested at n.u. (nitrates 20.14). Am I wise to dose phosphate? Redfield ratio?

Last issue, sulfur tested at 1044mg, and bromine tested at 75.64mg, with baselines being 794mg and 57.83mg respectively.

Thoughts appreciated!

 

[chipmunkofdoom2]

So I finally received my results back, and I am a bit concerned about some of the values - first being salinity. Test reported it at 30.21 PSU, my Apex and refractometer both test around 35-36.

Second issue - phosphorus vs phosphate. Phosphorus tested at 5.99 micrograms, while phosphate tested at n.u. (nitrates 20.14). Am I wise to dose phosphate? Redfield ratio?

Last issue, sulfur tested at 1044mg, and bromine tested at 75.64mg, with baselines being 794mg and 57.83mg respectively.

Thoughts appreciated!

When is the last time you calibrated your refractometer and your salinity probe with a quality salinity standard? The Apex probes have a reputation for not being the most accurate. Whether this is due to their implementation or the nature of conductivity probes, I can't say.

You should not attempt to maintain the Redfield ratio. At best, the Redfield ratio is only a guideline for use in reef aquaria, not a hard-and-fast rule.

Water changes would likely bring the sulfur and bromine down.

 

[Reefahholic]

Yeah, time to buy some calibration fluid.

 

[RockyProndoa]

Thanks for the reply.

I try to calibrate quarterly, or more, and in the case of the Apex, yes I agree the probe is typically more bother than it is worth. However, I do struggle a bit that both pieces of equipment would be off, and at the same amount, though I guess it is an equally difficult argument that the ICP test is wrong. Just seems strange.

The redfield ratio was just a suggestion on my part, I don't intend to copy it, merely mentioned it as a legitimate baseline to model. My bigger question is about the phosphorus vs. phosphate. ATI suggested dosing phosphates to achieve measurable readings - are phosphate/phosphorous independent of each other? As in if I raise phosphate, will phosphorus go up as well?

 

[RockyProndoa]

Yeah, time to buy some calibration fluid.

Perhaps. I'm definitely going to double check when I get home, but it does seem extremely odd that both refractometer and Apex show 35.5ish and were calibrated independently.

 

[Reefahholic]

Perhaps. I'm definitely going to double check when I get home, but it does seem extremely odd that both refractometer and Apex show 35.5ish and were calibrated independently.

Yeah that’s really odd that both are reading the same. Did you calibrate with bad fluid from the beginning?

 

[RockyProndoa]

Yeah that’s really odd that both are reading the same. Did you calibrate with bad fluid from the beginning?

Tested the refractometer when I got home, turns out that whenever I calibrated it last, I dialed it in to 30 instead of 35ppm, which is right on par with the ATI test. So, as a case of user error, I have been running my tank at 30 for the past 3-6 months. Still doesn't explain how the Apex probe got out of whack, but at least I can verify the ATI results.

I'll be using NSW as top off to slowly bring the value in line to 35ppm.

Now to figure out the phosphate dosing...