.1 ppm PO4 in fresh RODI Saltwater?

TCoach

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So, I've been having high phosphate in my tank (was up at 3ppm, now ~1.7ppm after a couple 30% wc's), and was curious about my fresh salt water. So I tested tonight with my Hannah ULR Phosphate, and it measured .1 ppm. Is this normal?

I'm guessing based on some searching here, that it may be my RODI water. But not really sure. I doubt it is my IO salt, as there would be a firestorm on the boards if this was the case. Overall high phosphate are probably a mix of 17 year old Fiji live rock and feeding frozen foods, but the water is not overly helping.

Anyway, thoughts on this? Do I need to use a GFO reactor or something of that sort on my fresh salt water before adding it to the DT? I'm just focused on trying to keep my tank parameters no higher than they now are and keep everyone happy and healthy.

Full parameters from today's testing.:
1624668355995.png


Thanks
 
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TexanCanuck

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Randy already discussed this in an earlier thread:

 

Randy Holmes-Farley

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The amount is not worth agonizing over about. It is a very minor contribution to the overall phosphate balance.


Comparison of Food Sources of Phosphate to Other Sources
What about other sources of phosphate, like the “crappy” RO/DI water containing 0.05 ppm phosphate? A similar analysis will show it equally unimportant relative to foods.

Let’s assume that the aquarist in question adds 1% of the total tank volume each day with RO/DI to replace evaporation. Simple math shows that the 0.05 ppm in the RO/DI becomes 0.0005 ppm added each day to the phosphate concentration in the aquarium. That dilution step is critical, taking a scary number like 0.05 ppm down to an almost meaningless 0.0005 ppm daily addition. Since that 0.0005 ppm is 40-600 times lower than the amount added each day in foods (Table 4), it does not seem worthy of the angst many aquarists put on such measurements. That said, tap water could have as much as 5 ppm phosphate, and that value could then become a dominating source of phosphate and would be quite problematic. Purifying tap water is important for this and many other reasons.
 

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