Phosphate readings

frank10 · Sep 16, 2020

Hanna ULM
day reading
1 0.15
2 0.09
4 0.14
5 0.49
7 0.01
8 0.04 (today)

Is the 0.35 swing from day 4 to 5 possible? Is a 0.48 swing from day 5 to 7 possible?

I'm thinking it was user error for day 5, but the skimmer was very active that day. I have a 150 gallon tank.

Shirak · Sep 16, 2020

Possible? I spose so. Did you do a second test on day 5? When I get a result that seems way out there I will repeat it to confirm. I may use a different test kit but in this case I wouldn't have since I think the Hanna ULM is the best for phosphate. You said the skimmer was more active that day so maybe something in the water that reacted with the test to give a higher reading but wasn't totally dissolved phosphates. Did you dose anything early that day or the day before? Or perhaps feed with something like a powdered food?

MERKEY · Sep 16, 2020

How old is your tank?

Did you start with dry rock?

Are you running a reactor?

.49 to .01 is a highly unlikely swing in 2 days unless there was a user error or something leaching phos which you would need to be removing it manually.

frank10 · Sep 16, 2020

Unfortunately, no second test that day

It's a year old, and no reactor

Albertan22 · Sep 16, 2020

Did you feed reefroids or something similar that day? That could cause a swing like that. I generally don’t test within a day of broadcast feeding coral food to the tank.

Shirak · Sep 16, 2020

I'm not so sure about user error. But possible. I would do 2 or 3 tests all in the same day on at the same time. If they are all very close to each other I would rule out user error. Maybe a run down on how you are doing the tests also would help. Every step you are doing.

I do note that your numbers are a little sort of all over the place .15 to .09 back to .14. I would typically see .02-.03 phosphate usage per day on my 60g with a refugium running too. What are your nitrate levels at? Perhaps your nitrate is on the low side and your phosphate is not being taken up by algae and corals at a steady pace?

And what are you feeding and dosing and how much/often in relation to your sampling for testing?