Reef nutrition

Phosphates in straight RODI water?

I have been chasing a higher than normal Phosphates issue in my tank. I tracked it down to the RODI water that I was using. The unit is 1 year old on membrane #1 and 6 months on membrane #2. The carbon block 1 micron filters have both been replaced. The Sediment 1 micron filter looks nearly spotless. I couldn't find a replacement in town. I took the water straight out of the rodi and used the hanna checker ULR *neon green* to check the water. I am getting a 0.24 reading. I am told this number should be 0?

I took a TDS reading manually several times and get 0PPM TDS.


Are my readings normal or do I need to keep changing stuff out in my BRS GPD-75 system (upgraded to 150 + RESIN/DI add-on filter)


- Randy
 



"foods are the primarily source of phosphate in almost any aquarium that is being fed, regardless of the choice of foods and rinsing etc. In most aquaria, this source dominates all other sources by a factor of ten to a hundred or more"


"Consequently, reef aquarists should expect that much of the phosphorus added to a reef aquarium in the form of foods ultimately ends up in the water as phosphate. Whether that portion getting into the water is 95% or 35% won’t substantially impact the conclusions below that foods add a very large amount of phosphate."
 
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"Conclusion​

Foods are by far the most important source of phosphate in most aquariums. While there are big variations between foods, it does not appear in this analysis that dry foods are the nasties they are often made out to be, relative to frozen foods. There are better and poorer choices (with respect to phosphate) to be made within each food type. Avoiding foods with bones, however, might be worthwhile if delivering less phosphate is a goal. Additionally, fresh grocery store shrimp seems to be one of the best foods from this standpoint.

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. It can be scary to learn that your purified fresh water has phosphate in it, or that your salt mix has detectable phosphate, or that your supplements or whatever have some phosphate. But just because you detect something, and maybe you even detect a concentration far higher than in your aquarium, that does not by any means imply that those sources are significant enough to warrant some sort of corrective action. Our analytical tools have become fairly sensitive, allowing us to detect things which might sound like trouble, but really aren’t. We need to understand the various dilution issues involved as well as the overall phosphate balance in a reef aquarium to evaluate the importance of different measurements.

Just use some math and put it all into perspective, before using some dollars or time to chase a trivial “problem”.

Happy Reefing"



Ultra pure water out of RODI will fool many test kits as it doesn't have the ions needed to make the reaction happen that the test kit is looking for. The bold at the bottom is the important part. Phosphate comes from food at 100x the rate of other methods, so that is your culprit. Feed less, GFO, lanthanum chloride, ATS, a big fuge will all work and have their own quirks.
 

"Conclusion​

Foods are by far the most important source of phosphate in most aquariums. While there are big variations between foods, it does not appear in this analysis that dry foods are the nasties they are often made out to be, relative to frozen foods. There are better and poorer choices (with respect to phosphate) to be made within each food type. Avoiding foods with bones, however, might be worthwhile if delivering less phosphate is a goal. Additionally, fresh grocery store shrimp seems to be one of the best foods from this standpoint.

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. It can be scary to learn that your purified fresh water has phosphate in it, or that your salt mix has detectable phosphate, or that your supplements or whatever have some phosphate. But just because you detect something, and maybe you even detect a concentration far higher than in your aquarium, that does not by any means imply that those sources are significant enough to warrant some sort of corrective action. Our analytical tools have become fairly sensitive, allowing us to detect things which might sound like trouble, but really aren’t. We need to understand the various dilution issues involved as well as the overall phosphate balance in a reef aquarium to evaluate the importance of different measurements.

Just use some math and put it all into perspective, before using some dollars or time to chase a trivial “problem”.

Happy Reefing"



Ultra pure water out of RODI will fool many test kits as it doesn't have the ions needed to make the reaction happen that the test kit is looking for. The bold at the bottom is the important part. Phosphate comes from food at 100x the rate of other methods, so that is your culprit. Feed less, GFO, lanthanum chloride, ATS, a big fuge will all work and have their own quirks.


I just want to let you know that the issue WAS that while the sediment filter looked good to the eye, it needed to be changed. Changed this out and boom I am within the margin of error for phosphates. 0.2

For the record I went with a 1/2 micron filter.
 
If your TDS is zero after the DI. You should have zero phosphates. It does not matter what your sediment filter is doing if TDS is zero out of the DI.
 
If your TDS is zero after the DI. You should have zero phosphates. It does not matter what your sediment filter is doing if TDS is zero out of the DI.

I totally agreed with Ian. Heck, even if your TDS is at 50, I doubt your PO4 will even registers on any test. The sediment and carbon filter does nothing for removing PO4. Only the membrane and DI does.
 
I totally agreed with Ian. Heck, even if your TDS is at 50, I doubt your PO4 will even registers on any test. The sediment and carbon filter does nothing for removing PO4. Only the membrane and DI does.

And even the membrane isn't great at removing it.... this is why DI is so critical to the process... always have 2ea DI's inline.

For those that can't have the waste of RODI.... and have the money to support just DI, do it!
 
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