Phosphates in my RODI??

[SallyWho]

Yesterday I posted a thread about some issues with my tank and somebody raised their eyebrows at my phosphate level. It's always been high. Well, I don't know why it never occurred to me before to test my RODI water, so I did. It was 0.63ppm! I'm making up some new RODI this morning, so I collected some straight from the outlet- 0.16ppm. My RODI filters are only a few months old- resin hasn't turned brown at all, and the TDS is zero. Now, the RODI that I tested yesterday at 0.63 came from a squirt bottle I fill up by dipping into the RODI barrel, and it has been sitting there for a while. Is it possible that higher number is due to leaching from the plastic? My mixing barrels are food grade ones, so I'm hoping THEY aren't leaching phosphates! When I make new saltwater in a couple days, I'll test that too just for kicks. But is there a way to get rid of phosphates in my RODI? My tank's always had 2.0+ ppm and I'd love to someday get that down enough to keep some things alive that right now I can't. Doing water changes that aren't already phosphorous-y would be helpful.

 

[rhitee93]

I don't know about phosphate, but I think some of our test kits will only work with saltwater. Check to make sure your phosphate kit will work with RODI water before you do too much.

 

[Dom]

I had a similar issue. To test phosphates, I added salt mix to 1 gallon of RODI. Once at the correct temperature and salinity, I tested phosphates. I don't know that saltwater kits can test fresh water. I would think not.

 

[SallyWho]

I don't know about phosphate, but I think some of our test kits will only work with saltwater. Check to make sure your phosphate kit will work with RODI water before you do too much.

I hadn't considered that! I just googled whether my hanna checker could do freshwater, and the one I use apparently can! And I'm using the correct reagent for it too.

 

[Randy Holmes-Farley Verified Community Expert]

Is it 0 ppm TDS?

0.16 ppm in the ro/di water is largely insignificant unless doing very large water changes.

Here's why:

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.

 

[SallyWho]

Is it 0 ppm TDS?

0.16 ppm in the ro/di water is largely insignificant unless doing very large water changes.

Here's why:

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.

That's a good article- took me back to my o-chem class in college! So the 0.16ppm in the fresh RODI isn't the end of the world? What about the 0.63 in the older water? I'm doing weekly water changes of around 20%- would adding new water that has more phos to begin with than some people have in their whole systems cause problems? Or do I need to cut back further on feedings? Thanks!

 

[Randy Holmes-Farley Verified Community Expert]

0 ppm tds shouldn’t have 0.6 ppm phosphate in it. Is it possible the di was depleted?

 

[SallyWho]

0 ppm tds shouldn’t have 0.6 ppm phosphate in it. Is it possible the di was deple

‍ Yeah, it's weird. If I look really close the first DI canister is juuuust starting to brown a little, but the 2nd DI canister is still fresh.

 

[SallyWho]

‍ Yeah, it's weird. If I look really close the first DI canister is juuuust starting to brown a little, but the 2nd DI canister is still fresh.

Lol, don't know why the SHRUG EMOJI turned into a gender declaration! IT WAS SUPPOSED TO BE A SHRUG!

 

[geologeek]

I have personally found the TRM1 TDS monitor to be inaccurate and this was confirmed when used alongside my commercial tds meter.

If I am honest, I believe the TRM -1 is actually a fake given these can be bought for peanuts on AliExpress and eBay.

Do you have another method of measuring TDS with a pen type meter?

These are on the same line with the TRM1 being the first probe after the DI stage and the out line of the dual TDS meter is immediately after it.......they should both read 0 but as you can see, the commercial unit shows 0ppm while the TRM-1 shows 8ppm!

I have faith in the commercial unit.....none whatsoever with the TRM-1

 

[davidm777]

0 ppm tds shouldn’t have 0.6 ppm phosphate in it. Is it possible the di was depleted?

I head that if there is 0 TDS there might still be silicates or phosphate but would be at low levels. If levels are high then it should be detected by the TDS reading. Is there any truth to this?

 

[easycoral]

RO filter element needs to be updated regularly

 

[Randy Holmes-Farley Verified Community Expert]

I head that if there is 0 TDS there might still be silicates or phosphate but would be at low levels. If levels are high then it should be detected by the TDS reading. Is there any truth to this?

0 ppm tds generally assures the levels are not too high, but there can be some. Note that a number like 0.05 ppm phosphate is insignificant compared to daily additions from foods which are far higher.

 

[Randy Holmes-Farley Verified Community Expert]

RO filter element needs to be updated regularly

I’m not sure what filter you are referring to.

 

[chase240sx]

Bet you’ll also find ammonia if you test it, the filters in your RODI need changing