po4 in Fresh Salt Water and RODI

[rowdyreefing]

Ok, I will try to explain this to the best of my ability. I am finding po4 in my newly mixed salt and fresh RODI.

What I have done:
-got new batch of salt, tested both. Both have po4
-replaced DI resign, old and new both reading 0tds
-vinegar bathed mixing container, pump, and hose, still got po4 reading
-bought new brute mixing container, still got a po4 reading
-replaced battery in hanna checker, po4 readings were much lower after this
-used multiple cuvettes, found some inconsistencies between cuvettes

I have read several post that state the hanna checkers do not accurately test po4 in RODI. This would make sense as my po4 readings vary a lot when I have tested the po4 in RODI. So question 1, since my TDS is 0, should I not be concerned about the po4 reading in my RODI?

Second question. I am getting readings that my salt is mixing anywhere from 0.03ppm to 0.09ppm. I have never had high po4 issues in my tanks. Should I be concerned?

Third question. If the po4 reading is an issue, what should I do?

Please let me know if there is anymore information I should provide. Thanks in advance!

 

[Mellotang]

What salt mix?

 

[rowdyreefing]

What salt mix?

IO, and I know there are issues with this salt reported, but as I said I have never had po4 issues in my actual tank.

 

[Randy Holmes-Farley]

Phosphate is among the harder ions to hold on a DI, and <1 ppm TDS does not preclude the presence of something that is far less than 1 ppm, but none of those values (0.00-0.10 ppm phosphate in new salt water or RO/DI) are a concern:

Aquarium Chemistry: Phosphate And Math: Yes You Need To Understand Both

Foods are by far the most important source of phosphate in most aquariums. In considering whether sources of phosphate other than foods are important, one must carefully look to the actual amounts involved to determine whether other sources are even worth trying to minimize.

reefs.com

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.

 

[rowdyreefing]

Phosphate is among the harder ions to hold on a DI, and <1 ppm TDS does not preclude the presence of something that is far less than 1 ppm, but none of those values (0.00-0.10 ppm phosphate in new salt water or RO/DI) are a concern:

Aquarium Chemistry: Phosphate And Math: Yes You Need To Understand Both

Foods are by far the most important source of phosphate in most aquariums. In considering whether sources of phosphate other than foods are important, one must carefully look to the actual amounts involved to determine whether other sources are even worth trying to minimize.

reefs.com

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.

Thank you so much for the response. I have seen you post this multiple times, so I apologize for the repost.

With that being said, at what level po4 would be a concern with newly mixed salt? What is the goal for newly mixed SW <0.1??

Also, do you feel that 0.00ppm po4 newly mixed salt is not a thing?

 

[Randy Holmes-Farley]

Thank you so much for the response. I have seen you post this multiple times, so I apologize for the repost.

With that being said, at what level po4 would be a concern with newly mixed salt? What is the goal for newly mixed SW <0.1??

Also, do you feel that 0.00ppm po4 newly mixed salt is not a thing?

If the tank does not have excessive phosphate, then no level in the RO/DI or new salt water is a concern.

Certainly some folks will not see phosphate in new salt water. Many folks use source water before the RO/DI that doesn't have substantial phosphate, but in other cases it could be more than 1 ppm.

 

[rowdyreefing]

If the tank does not have excessive phosphate, then no level in the RO/DI or new salt water is a concern.

Certainly some folks will not see phosphate in new salt water. Many folks use source water before the RO/DI that doesn't have substantial phosphate, but in other cases it could be more than 1 ppm.

So is it safe to assume that there is no need to test po4 in new SW until there is an issue with the tank po4 levels?

 

[Randy Holmes-Farley]

So is it safe to assume that there is no need to test po4 in new SW until there is an issue with the tank po4 levels?

I certainly would not test 0 ppm TDS water for anything without evidence of a problem.