Why do I show elevated phosphates right after a water change?

optimisticdingo · Jun 13, 2021

So I've noticed that if I test phosphate directly after a water change I read elevated levels. If I check the next day the levels are more normal to what my tank has been reading.

I'm using the Hanna Phosphate checker, the standard one not the ULR.

In my 116 gallon my Phosphate was at .6ppm, after a 30% water change I checked and Phosphate was over 2ppm. I checked the next morning and it was down to .22. I'm not using a refugium or GFO so it seems that the levels elevate right after a water change. Any idea what causes this?

vetteguy53081 · Jun 13, 2021

Worst time to test is right after a water change when the tank is agitated from activity. Wait 12 hrs and reattempt test

blasterman · Jun 13, 2021

Have you tested your salt mix?

optimisticdingo · Jun 13, 2021

blasterman said:
Have you tested your salt mix?

No. It's Tropic Marin Pro Reef Salt

GoVols · Jun 13, 2021

vetteguy53081 said:
Worst time to test is right after a water change when the tank is agitated from activity. Wait 12 hrs and reattempt test

+1

LisaAP · Jun 13, 2021

I found the same, Tropic Marin Pro Reef is not phosphate free. I found as much as 0.1ppm on freshly mixed TMPR using the Hanna ULR tester. However that wouldn’t account for the difference you are currently seeing after a water change.

optimisticdingo · Jun 13, 2021

LisaAP said:
I found the same, Tropic Marin Pro Reef is not phosphate free. I found as much as 0.1ppm on freshly mixed TMPR using the Hanna ULR tester. However that wouldn’t account for the difference you are current seeing after a water change.

It's probably just due to the water being disturbed and it throwing the readings off

LisaAP · Jun 13, 2021

optimisticdingo said:
It's probably just due to the water being disturbed and it throwing the readings off

Possibly.

Randy Holmes-Farley · Jun 14, 2021

I'd check the water change water (raw tap water could do it, but not 0 ppm TDS RO/DI).

Otherwise, I'm suspicious that the result is test error.

optimisticdingo · Jun 15, 2021

Randy Holmes-Farley said:
I'd check the water change water (raw tap water could do it, but not 0 ppm TDS RO/DI).

Otherwise, I'm suspicious that the result is test error.

The water is 0ppm TDS RO/DI. I'm using the four stage BRS 150GPD system.

However, I've heard that plastics can release Phosphates and I store the water in plastic containers. Could this be the issue?

Randy Holmes-Farley · Jun 15, 2021

optimisticdingo said:
The water is 0ppm TDS RO/DI. I'm using the four stage BRS 150GPD system.

However, I've heard that plastics can release Phosphates and I store the water in plastic containers. Could this be the issue?

Possible, but not super likely, IMO.

Anyway, test the new water to see.