Phosphates always more than 0

ehap.spam · Apr 28, 2023

Sorry if posted in the wrong place. But I've been using the API test kits to measure phosphate and noticed I'm always getting back more than 0 back as a reading. Thought it was weird so I tested distilled water and it looks roughly the same.. 0.25-.5
Are my eyes off? Do you think the test solution went bad? Expiration date is 05/2025.

exnisstech · Apr 28, 2023

I'm not sure but it looks like the range on that test kit is not broad enough for normal reef levels of phosphates. My tanks run around 0.02ish which would most likely show up as zero on that test kit. 0.25 is the lowest reading next to zero available on that API kit so I would expect most tanks would show 0 because 0.25 is pretty high, at least compared to where mine run.
EDIT: it also states it is for freshwater

ehap.spam · Apr 28, 2023

exnisstech said:
I'm not sure but it looks like the range on that test kit is not broad enough for normal reef levels of phosphates. My tanks run around 0.02ish which would most likely show up as zero on that test kit. 0.25 is the lowest reading next to zero available on that API kit so I would expect most tanks would show 0 because 0.25 is pretty high, at least compared to where mine run.
EDIT: it also states it is for freshwater

Ah very interesting. The test in the images was for freshwater because I was trying to show how distilled (freshwater) is appearing to show up as more than 0, which I thought it was odd considering it's supposed to be pure.

EeyoreIsMySpiritAnimal · Apr 28, 2023

Why do you want 0 phosphate anyway?

EeyoreIsMySpiritAnimal · Apr 28, 2023

exnisstech said:
I'm not sure but it looks like the range on that test kit is not broad enough for normal reef levels of phosphates. My tanks run around 0.02ish which would most likely show up as zero on that test kit. 0.25 is the lowest reading next to zero available on that API kit so I would expect most tanks would show 0 because 0.25 is pretty high, at least compared to where mine run.
EDIT: it also states it is for freshwater

Phos of 0.25 is only "pretty high" in an ULNS system. P of 0.25 with N of 25 is fairly balanced...

ehap.spam · Apr 28, 2023

EeyoreIsMySpiritAnimal said:
Why do you want 0 phosphate anyway?

I guess I'm more concerned with the accuracy of the tests. Seems like pure water should show up a bit lighter than that. The main concern is that I want to make sure I'm starting with pure water for when I do water changes etc.

ehap.spam · Apr 28, 2023

EeyoreIsMySpiritAnimal said:
Phos of 0.25 is only "pretty high" in an ULNS system. P of 0.25 with N of 25 is fairly balanced...

My point is it seems pretty high for water I expect to be pure

doubleshot00 · Apr 28, 2023

ehap.spam said:
I guess I'm more concerned with the accuracy of the tests. Seems like pure water should show up a bit lighter than that. The main concern is that I want to make sure I'm starting with pure water for when I do water changes etc.

Api sucks. Idk what else to say here.
How does the tank look.

gbroadbridge · Apr 28, 2023

ehap.spam said:
Sorry if posted in the wrong place. But I've been using the API test kits to measure phosphate and noticed I'm always getting back more than 0 back as a reading. Thought it was weird so I tested distilled water and it looks roughly the same.. 0.25-.5
Are my eyes off? Do you think the test solution went bad? Expiration date is 05/2025.

It's a useless kit for Marine tanks anyway, so it really does not matter what the results are

EeyoreIsMySpiritAnimal · Apr 29, 2023

ehap.spam said:
My point is it seems pretty high for water I expect to be pure

Use RODI, not grocery store distilled water...

Spare time · Apr 29, 2023

API phosphate test is useless. Get a new test kit before doing anything. The difference between 0 and 0.25 is huge and it can't tell the difference.

Spare time · Apr 29, 2023

EeyoreIsMySpiritAnimal said:
Use RODI, not grocery store distilled water...

Distilled water doesn't contain phosphate

EeyoreIsMySpiritAnimal · Apr 29, 2023

Spare time said:
Distilled water doesn't contain phosphate

Unless the "distiller" did it wrong. My point is you don't really know how well the water was filtered unless you don't yourself ...

ehap.spam · May 4, 2023

Spare time said:
Distilled water doesn't contain phosphate

My thoughts exactly, which is why I was so confused.

Spare time · May 4, 2023

ehap.spam said:
My thoughts exactly, which is why I was so confused.

Its actually more pure than RODI water from my understanding.

shadyraro · May 5, 2023

Do you have a TDS meter to test the distilled water? Pretty sure it won’t be zero like RO water should be.

Randy Holmes-Farley · May 5, 2023

Spare time said:
Its actually more pure than RODI water from my understanding.

It can vary, depending on how exactly it is made, and what is done with it after purification.

GARRIGA · May 5, 2023

I’ve bottomed my nutrients out and my API phosphate read zero. Could be expired regent. API isn’t precise but close enough. Not all grow Acro or require 0.03 ppm.

Best option is buying a reference solution or creating your own with NeoPhos or its generic equivalent to measure approximate accuracy. No hobby test kit going to be precise, either.