ICP Result Suggestions

[DenaliDan]

I recently received the results of my first ATI ICP test. Not too surprised by anything other than the Phosphorus/Phosphate readings. I've done a bit of searching around here and do see where the ICP results for these nutrients cannot trusted much but I have not found any posts that explain a difference quite like mine. Below is the ICP results vs the Hanna tests I took on the same water collection date. My Hanna PO4 tests have finally been somewhat consistent lately after struggling for the last year so a bit alarmed about this discrepancy. Additionally, ATI ICP showed my silicon was high and recommends I use an iron-based PO4 absorber to adjust. I don't want to take a knee-jerk reaction here so would appreciate any advice.

	ICP	Hanna
NO3	32.25 mg/l	20.6 ppm​
	Ideal value: 2.00 mg/l
P	176.2 µg/l	not tested
	Ideal value: 14.16 µg/l
PO4	0.54 mg/l	0.16 ppm​
	Ideal value: 0.04 mg/l

 

[Oldreefer44]

My response would be to ask: How does everything look in your tank? Are there symptoms of issues that are apparent that you want to address? I

 

[DenaliDan]

I did consider that approach and yes, there are some issues. My tank does not seem to be doing as well as I'd expect at 15 months. Hardly any of the coral seems to be thriving. Most seem to be surviving. Of course, I've lost quite a bit along the way to various symptoms. I'm just trying to determine what to do, if anything, with the data from the ICP test.

 

[Pod_01]

Just a quick comment, ICP doesn’t test NO3 or PO4.
For these measurements the company uses similar test to the one you use at home.

Looking at the results I would say NO3 is reasonably close.
The PO4, did you collect and test at the same time?
If not feeding could impact the measurement. I usually collect and test at the same time and I try to do it in the morning before feeding or late at night.

If the tank looks good I would be inclined to sit on my hands.

 

[Oldreefer44]

IMO more damage is done from overreacting to test results that the other way around. I run ICP test every 4 to six weeks and never make adjustments based on just one unless there is a major issue. At this point unless you are having major algae issues I would work more on consistency in parameters than trying to hit a certain number. Many long time hobbyists get great growth with higher numbers than you have. If and when you do try to make an adjustment through by dosing or GFO etc. my recommendation, based on several decades in the hobby, is to go slow and never do more than one at a time.

 

[Randy Holmes-Farley]

There's never a reason to try to alter silicate/Si values unless you have a problematic level of diatoms. If you do not, I'd ignore it.

The nitrate values are likely in agreement within test error of the methods used, or pretty close anyway.

Phosphate may be worth lowering with either value, but there are many tanks with elevated phosphate that are quite nice and I wouldn't agonize over it.