chemi clean and phosphates


New member
Would a treatment with chemi clean suck out all phosphates to give a reading of 0.00 on a Hanna 713 4-5 days after treatment? Never used a Hanna before and was surprised with that reading. I assume it's because of the treatment?


In Memoriam
no thats not possible. interfering with the test kit would be a new phenomena I hadnt heard of, that could make a bad reading, but as far as literally acting on phosphates nope.

Reef Frog

New member
Right. I don't see how it could directly affect any test either.

Assuming you previously measured high phosphates or had an algae outbreak, I cant imagine a bag of CPE could bring PO4 down like that in a 180g. Maybe I'm missing something but I think a testing error of some kind occurred, assuming you had measurable PO4 in the first place.


New member
Unless your tank was totally nitrate blocked, or a swamp, phosphate readings are pretty rare. This stuff is for algae what candy is for kids. Even if your phosphates are through the roof your test will often still read zero since algae mops it up so fast. Almost none of the commercially avaliable tests check for organic phosphate. It is one of those things that I never test for. Checking for a small patch of hair algae or cyano is a far better "test". Once you see one of those it is time to change your GFO.

Btw, did you get the Hanna checker because you did not trust your old test?


New member
Yes, all I've had up to this point is API phosphate test kit. I've used it maybe once in 2 years.

That might be why you had a jump in phosphates but I am no expert in those tests since I never use them. Don't know if Hanna measures organic phosphate.

Might be an excuse for being lazy but I find that algae growth is the best phosphate test there is.


ReefKeeping Mag staff
Premium Member
Chemi clean or do you possibly mean chemi pure? The chemi pure elite contains gfo. Chemi clean might oxidize some sludge and have an indirect effect but I don't know that for certain.

Many tanks show significant othro phospahte with or sometimes wit hout much algae. I think testing for it is prudent.