.05 phosphate in salt...

[TD13]

so I have been battling a phosphate issue and couldn't figure out why. Seemed every time I did a water change it bounced up. Come to find out the salt I'm using contains a fair amount of po4. I used a Hanna meter and caught water straight from the RODI and tested from my RO storage, both = 0.00. Mixed some salt to 1.026 and BAM!!!! Po4 at .05 from the same tub I just tested at 0. Anyone else have this issue?

 

[Sabellafella]

Ehat kinda salt u use

 

[Tegridy Reef]

I had a felling glad some one was able to test it salt is so un clean great research would b nice to know what salt

 

[Nathan Froehner]

What type of mix?

 

[Randy Holmes-Farley Verified Community Expert]

It doesn't matter since that amount is too small to be important, whether it is real or just testing error. Even if real, you put in way, way more with foods than water changes with a mix that contains 0.05 ppm phosphate.

I address that sort of issue here:

http://www.advancedaquarist.com/2012/3/chemistry

from it:

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.