Phosphate tests

Matthias7 · Aug 18, 2016

i have been using a Hannah phosphate checker for a year or two. I recently had an issue with it. I test phosphates every few months or so the last test I read was in the normal range 0.02. I decided to test it again and it was 0.12. I decided to do nothing with this second reading. I retested again a few days later and the initial test was 0.2. At this point I decided to run some GFO (just a small amount, tank and support tanks total around 350 gallons). I tested again 1 day after the gfo was added and the result was 0.00. Once again retested and got the same result 0.00.
I then decided to go buy a cheap Api phosphate test. The test result was also 0.
My tank looks pretty good very minimal algae growth have to clean the glass maybe once a week usually longer. I do run a refugium with lots of chaeto and mangroves. I guess my question is which test should I go with. Anyone else have great fluctuations like this?

Elementalj · Aug 18, 2016

I've used Hanna test kits too. Had similar issues with the calcium checker over a single drop of water. Maybe it was just a fluke? And as for the API kit, they both use a titration to generate a reading so I'd assume they're very similar and should generate similar results.

Randy Holmes-Farley · Aug 19, 2016

There may be a testing issue, but it is also possible the phosphate rose then got knocked back by the GFO.

Matthias7 · Aug 19, 2016

Tested again today using both the Hannah and the Api. Both results were 0 again. I ordered a salifert just for comparisons sake. My concerns are for my sps which have some recession at the bases on the bigger prices and growth at the tips on all peices. Lighting and flow have changed significantly recently as well so maybe impossible to pin point the issue.

Randy Holmes-Farley · Aug 20, 2016

I'd back off on the GFO.

Matthias7 · Aug 25, 2016

Well added a salifert phosphate kit to my collection. It also tested 0. Not sure why I find it hard to believe, but I do. I guess that explains why my corals don't look so good at 9 dkh. Backed it down to 8 for now gfo offline as well