Am I misinterpreting Phosphate in RO/DI Guidance?

[threebuoys]

@Randy Holmes-Farley I have read through a number of threads and some of your articles concerning phosphate management and I want to be sure I'm interpreting the info correctly.

Using the Hanna ULR phosphate checker, I have determined my phosphate level is 0.49 ppm, or about 10 times higher than the typical target for a reef aquarium.

I also determined my freshly mixed saltwater is at a level of 0.30 ppm. I assume most of this is likely due to the RO/DI water I'm using, but I do not have a testing device for phosphates in fresh water.

I believe your position on phosphates in RO/DI is that the level I am experiencing is within an acceptable range for RO/DI and that from a phosphate management perspective, I should focus on nutrient load in the tank since that will most likely be the source of any problems I might encounter now or in the future.

To manage phosphate levels going forward, I'm in the process of adding a GFO reactor to the system. I've read your article that describes various ways to address high phosphate levels, and this one seems to be a reasonable way to start since my levels are not off the charts yet.

If I target a level of around 0.03 ppm, phosphates should not be an issue for corals typically added to a reef tank?

I ask because my tank is relatively new (9 months) and I've only started adding corals in the past 3 months. All are alive, but some look a little puny and some threads suggest high phosphate levels can affect color and fullness of some corals. I'm trying to avoid a potential future problem.

So, should I also be considering other issues before I move forward with a GFO reactor?

 

[Rmckoy]

@Randy Holmes-Farley I have read through a number of threads and some of your articles concerning phosphate management and I want to be sure I'm interpreting the info correctly.

Using the Hanna ULR phosphate checker, I have determined my phosphate level is 0.49 ppm, or about 10 times higher than the typical target for a reef aquarium.

I also determined my freshly mixed saltwater is at a level of 0.30 ppm. I assume most of this is likely due to the RO/DI water I'm using, but I do not have a testing device for phosphates in fresh water.

I believe your position on phosphates in RO/DI is that the level I am experiencing is within an acceptable range for RO/DI and that from a phosphate management perspective, I should focus on nutrient load in the tank since that will most likely be the source of any problems I might encounter now or in the future.

To manage phosphate levels going forward, I'm in the process of adding a GFO reactor to the system. I've read your article that describes various ways to address high phosphate levels, and this one seems to be a reasonable way to start since my levels are not off the charts yet.

If I target a level of around 0.03 ppm, phosphates should not be an issue for corals typically added to a reef tank?

I ask because my tank is relatively new (9 months) and I've only started adding corals in the past 3 months. All are alive, but some look a little puny and some threads suggest high phosphate levels can affect color and fullness of some corals. I'm trying to avoid a potential future problem.

So, should I also be considering other issues before I move forward with a GFO reactor?

I recently did the same .
tested freshwater from the rodi system with the Hanna phosphorus ulr checker and got .030ppm
The dt was at .7 ppm .
I added rowaphos and carbon in 2 separate reactors but the recommended amount was 1 table spoon per 10 gal
I went with the one table spoon carbon per 10 gal but 1/2 table spoon per 10 gal rowaphos

lowering too fast is never a good thing ...

 

[threebuoys]

@Randy Holmes-Farley

Am I understanding correctly?

Thanks

 

[Randy Holmes-Farley]

0.3 ppm phosphate is getting borderline high in Ro/DI.

Are you monitoring the effluent for TDS?

it is still not the biggest contributor in a fed tank, but is becoming significant.

 

[threebuoys]

0.3 ppm phosphate is getting borderline high in Ro/DI.

Are you monitoring the effluent for TDS?

it is still not the biggest contributor in a fed tank, but is becoming significant.

I thought it was high too, I just changed out the filter canisters in the RO/DI system. The RO/DI is only used for the aquarium. I thought that might help explain the high level in the display tank, however, the .3 phosphate reading for RO/DI was after the canister change-out.

County water tds = 321 ppm, after 6 stage RO/DI tds = 1 ppm.

Part of the reason I've ordered the GFO reactor, I'm concerned that water changes and ATO are both adding more phosphate than the target level so it seems I'm fighting a losing battle.

I would prefer to remove the phosphate with the RO/DI but not sure how to do that. Add another canister? Which one?

 

[Randy Holmes-Farley]

I thought it was high too, I just changed out the filter canisters in the RO/DI system. The RO/DI is only used for the aquarium. I thought that might help explain the high level in the display tank, however, the .3 phosphate reading for RO/DI was after the canister change-out.

County water tds = 321 ppm, after 6 stage RO/DI tds = 1 ppm.

Part of the reason I've ordered the GFO reactor, I'm concerned that water changes and ATO are both adding more phosphate than the target level so it seems I'm fighting a losing battle.

I would prefer to remove the phosphate with the RO/DI but not sure how to do that. Add another canister? Which one?

I'd personally use a second DI to drop the TDS to zero if I was trying to reduce phosphate.

Just for clarification, the phosphate being higher in top off and water changes than the tank target does not mean it is significant. But 0.3 ppm is becoming substantial, if accurate. 0.05 ppm is not, IMO. I discuss that exact topic here:

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 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.