View Full Version : New Hanna Phosphate Checker and 0.00 ppm measurements - is my meter broken?

10/02/2012, 09:29 PM
I finally purchased a Hanna Phosphate checker after battling algae for the last year or so. I followed the directions and measured 0.00 ppm the first time. I thought I rushed it so I went through the procedure again (w/o reagent) and verified it against the online instructions. Everything checked out. So I then proceeded to measure my tank again taking my time, cutting 2 sides, funnel, etc. Again, 0.00 ppm. I then tested new make up water and that checked out at 0.00 ppm. While I have been running BRS GFO and replace it every other week or so I'm finding it difficult to believe that I'm at 0.00 ppm. Although because I had ich in March I've been fishless until a few weeks ago and I've been feeding just enough for my one percula clown fish. It makes me question whether or not the Hanna meter is working correctly.

Am I making to much of this? Should I be content that the measurements are correct? If my phosphate levels really are 0.00 ppm I imagine that is not good either. Should I back off the BRS to allow the readings to come up to 0.02 - 0.03?

10/02/2012, 09:49 PM
phosphate checker is not quiet reliable at ultra low range. a hanna phosphorus ultra low checker is. also if there is algae and its consuming phos as being produced it will not register on any test kit.

10/02/2012, 10:25 PM
It's only rated as being accurate to +/- 0.04 ppm, so a zero reading seems reasonable to me. That's fairly common.

10/03/2012, 01:36 AM
Yes -- I did the same thing. I purchased a phosphate test kit when I realized I had algae problems (in my case a RedSea pro), only I have never gotten a phosphate reading. Always zero.

The growing algae eats up the phosphate as soon as it appears. The only thing I can figure out is that phosphate kits are for people who don't yet have algae and want to keep it away. There must be a 'lag time' after phosphate appears before the algae takes hold and you can avoid it if you test and eliminate it in this time.

10/03/2012, 04:21 PM
A phosphate test kit can be useful for diagnosing problems with stony coral, since phosphate can interfere with their growth. Sometimes they're useful for algae problems, when they give an idea of how much free phosphate there is in the system. Some approaches are more useful when the phosphate is very high.

10/03/2012, 06:27 PM
you can try testing a small batch of water you know contains phosphates, ie a cup of cup of water with food in it. use something where it wouldnt be a pain to make sure food doesnt get into the test vial

10/03/2012, 08:17 PM
Switching out GFO weekly may very well cause you to approach zero. We get near zero readings with the Checker and 4 weeks is the average for us to change GFO.

10/03/2012, 08:21 PM
Thanks for all of the responses.
I should have looked a the specs. a bit closer. I've been reading up on vodka dosing and thought I would need this for the start of that testing in order to identify a drop. But that is an entirely different discussion.

10/03/2012, 09:07 PM
You're welcome!

10/04/2012, 07:55 AM
Something sounds fishy to me. I have gotten a 0 reading once or twice, but it is rare. And I doubt your PO is that low consistently. Check your tap water.