ro/di and phosphates

[reefmaster70]

so, I've been tring to adjust my Nitrates and Phosphates in my 6 months old 75g reef tank now for a few months. Currently dosing NoPox...and am lowering the numbers on my tank, but tonight I decided to check my Nitrates and Phosphates on my RO/DI water. I do these maybe twice a year. I just changed out my RO Membrane, so it's new (a few weeks old). and I also have dual DI resin beds running at the end of the process. My TDS meter reads out 0ppm. I tested my Nitrates tonight and not surprisingly they are at 0.0ppm, which I fully expected. Next I test Phosphates, and I expected another very low number as well....when my Hanna checker timed out it read .14ppm..I was shocked. I actually had the checker re-read the test again and same result. I could see no visual blueish tint at all...just some very small undissolved particles floating around in the test cuvette. Could particles throw the test off? Could my fresh RO/DI water really have Phosphates of .14, esepcially running through two new dual DI resin units? Pressure through my unit is also around 85psi.

Any thoughts would be great. Thanks

 

[Randy Holmes-Farley Verified Community Expert]

That level is largely insignificant relative to the far higher amount you add in foods each day. You can drive it down in the to/di with a second di, but that reason is not worth it, IMO.

https://reefs.com/magazine/aquarium-chemistry-phosphate-and-math-yes-you-need-to-understand-both/

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 watercould 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.

 

[James Franco]

Have you given Chemipure Elite or Blue a try?

 

[Christoph]

That level is largely insignificant relative to the far higher amount you add in foods each day. You can drive it down in the to/di with a second di, but that reason is not worth it, IMO.

https://reefs.com/magazine/aquarium-chemistry-phosphate-and-math-yes-you-need-to-understand-both/

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 watercould 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.

very true, feeding is the #1 wy of introduction of phosphorus/phosphate.

We have measured the total phosphorus content of various feeds, and calculated a theoretical phosphate rise if all the phosphorus contained in the feeds is converted to phosphate. The feeding amount is 1g per 100l of water volume, x axis is mg/l Phosphate.

Left is dry food (pellets, mixed flakes, spirulina flakes), right is frozen food (which also shows lower levels because of residual water content).

all the best, Christoph

 

[Randy Holmes-Farley Verified Community Expert]

Have you given Chemipure Elite or Blue a try?

Chemipure blue will not bind phosphate from seawater. GFO will, and is a component in the elite.

 

[Randy Holmes-Farley Verified Community Expert]

very true, feeding is the #1 wy of introduction of phosphorus/phosphate.

We have measured the total phosphorus content of various feeds, and calculated a theoretical phosphate rise if all the phosphorus contained in the feeds is converted to phosphate. The feeding amount is 1g per 100l of water volume, x axis is mg/l Phosphate.

Left is dry food (pellets, mixed flakes, spirulina flakes), right is frozen food (which also shows lower levels because of residual water content).

all the best, Christoph

Thanks, Christoph. :)