phosphate question

foxhuntr · Jan 26, 2015

I did some testing because i am having phosphate problems.....i changed all my filters and resin on my rodi unit....i filled my brute can with ro water and tested it. It came out with 0.12ppm....them i tested the water coming out of the ro line and it came out at 0.29ppm.....is it possible for the ro line to be holding or leaching phosphate ? I have never change the hose yet.i just think it is kinda weird that the phosphate is lower in my salt mixing container than it is coming out of the ro hose.....all testing in done with a hanna tester with regent good until 6/16.....

Randy Holmes-Farley · Jan 26, 2015

Are you monitoring the TDS?

zebe00 · Jan 26, 2015

I would purchase another test kit to justify the number from the Hanna. I have one, and its usually accurate, but I have had it read oddly high before only to test with Red Sea right afterward and get a reading of 0.00 ppm.

foxhuntr · Jan 26, 2015

Yes my TDS meter is reading 000....i know my phosphates are hihh because i am getting algae blumes

Randy Holmes-Farley · Jan 26, 2015

If the TDS is 0 ppm, then it is unlikely that the RO/DI water is the primary source. Even if the RO/DI is 0.1 ppm (and I expect it is not), it is way less than you add each day in foods. Maybe 10-100 times less. Foods are the source to worry about.

When phosphate is elevated, the best thing to do is look at the export side of the equation, assuming you are not using tap water or feeding too heavily. Something like GFO or one of the other ways of reducing phosphate, such as growing macroalgae or organic carbon dosing.

foxhuntr · Jan 29, 2015

Ok....this is really driving me insane.....i still have phosphates in the range of .09 ppm in my ro water.....thats before i even mix my salt into it ....i just changed my carbon filters, my ro membrane and my di resin.....i ran out about 3 gallons of ro water to flush the lines and holding tank......i took a reading with my hanna with new regents and got .09 ppm......just for the hell of it i took a reading at my kitchen faucet and got .19 ppm.......dont understand where the phosphates are coming from.....i just bought a elos test kit to double check my readings and i get below detectable.......i just thought of something .......will my hanna work on fresh water ?

UK_Pete · Jan 29, 2015

Clean the vials real well just before you put them in the tester, using a dry tissue. What I do is fill the vials with tank water, put the sachet in one vial, cap them both, wash them under the tap, dry with a towel, buff them with a tissue. Then put one vial in and zero the tester with it, polish it with tissue just before you put it in as finger prints mess with the readings (dont touch the glass after buffing it, hold by the cap). Then do the other vial, buffing before putting it in again. While hanna say use the same vial for zeroing and testing, I find with my clean scratch free vials I can use one vial to zero and one to test, which makes the whole process easier. Keep an eye on the time, ideally you want to shake for 2 mins, then rest for 3 mins, before taking the reading. Think it all through before hand so you know exactly the process. Its really easy to get bad results with the hanna I find, from dirt or prints on the glass. IF you still have problems soak the vials in strong hydrochloric acid for a hour or so (de-scaler might work if you dont have hydrochloric). Keep the vials pristine too otherwise the above wont work and even using the same vial wont work well with anything but a clean perfect vial.

foxhuntr · Jan 29, 2015

Thanks UK Pete.......i did another test with 2 vials one to zero and the other with regent......i did notice the way i was doing it before the water was alittle cloudy when putting in the hanna so that was setting off my readings.......i let it rest for a couple minutes to clear up....this time i got .03 ppm....i would really like to get .00 ppm.....

Randy Holmes-Farley · Jan 29, 2015

That phosphate is not significant, even if real. A single feeding adds tens to hundreds of times as much phosphate as 0.05 ppm phosphate top off water. I've shown this mathematically, so it is not worth worrying about, even if real.

Randy Holmes-Farley · Jan 29, 2015

This is the article I'm referring to:

Aquarium Chemistry: Phosphate And Math: Yes You Need To Understand Both ? Advanced Aquarist | Aquarist Magazine and Blog

from it:

[h=2]Comparison of Food Sources of Phosphate to Other Sources[/h]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.