Hanna Phos Checker reading 0?

LesPoissons · Jan 5, 2020

Hey guys,
Got the Hanna checker for my phosphate since the color chart w the test kit is just too annoying to read. I keep getting readings of 0.00 though. (Ran it 3x- followed simple directions.) Does anybody else get zero readings for phos? That seems like it would be inaccurate? (It is the low range phosphate test.) thanks!

cmaxwell39 · Jan 5, 2020

It is very possible to have 0 phosphate, although it is not advisable to maintain phosphate that low. Tell us a little more about your system. Tank/system size, stocking, nutrient export methods, feeding amounts etc.

LesPoissons · Jan 5, 2020

It’s a 220 gallon tank, mixed reef w lps and sps and softies. 4 years old ish. 55g sump with skimmer, fuge, gfo/carbon reactor and uv. I use filter socks just to help with micro bubbles so they usually stay on for a week or more at a time. Nitrates consistently stay 2-5 (salifert). I usually feed at least twice a day and if anything I probably overfeed bc of the dog face puffer. There’s also tangs, angels, clowns, chromis, dart fish, gobies, trigger, nems etc. I currently run GFO because I was getting higher phosphate readings on my test kits and I’m having algae issues. (Build up on the glass a day after scraping, Red cyano, I have diatoms on the sand, etc). My other test kit was hard to read but it was never 0 as far as I could tell. Idk it seems unlikely that there’s 0 phos in that tank? I’m not trying to maintain ultra low nutrients, I think low levels are important for corals, I just wanted to accurately know where the tank is currently- That’s why am surprised that the Hanna checker is saying that my Phos is zero?

PatW · Jan 5, 2020

i maintain phosphate pretty low and I often get reading of 0. For low nutrient systems, you want less than .03 ppm but more than 0.

If you are using GFO, it is easy to quickly strip the phosphate from the water.

Your easiest option for checking your checker is to find a LFS that routinely measures phosphate and have them measure your water. Also, you could measure some of their water with a known phosphate reading to cross check.

If that is not an option, your best recourse is to buy some phosphate salt and mix up a standard solution with a known concentration.

cmaxwell39 · Jan 5, 2020

PatW said:
i maintain phosphate pretty low and I often get reading of 0. For low nutrient systems, you want less than .03 ppm but more than 0.

If you are using GFO, it is easy to quickly strip the phosphate from the water.

Your easiest option for checking your checker is to find a LFS that routinely measures phosphate and have them measure your water. Also, you could measure some of their water with a known phosphate reading to cross check.

If that is not an option, your best recourse is to buy some phosphate salt and mix up a standard solution with a known concentration.

I agree with all of the above. Another way to double check your Hannah meter is to purchase their calibration check set to make sure that your meter is reading a known phosphate solution accurately.

HI713-11 Phosphate Calibration Check Set for HI713 Checker

Easily calibrate and test proper functionality of your Hanna Checker HI713 Phosphate Low Range for fresh and marine water (saltwater). Contains Standard A, Standard B and 1 Packet 713-25 Reagent* Follow instructions in packaging Acceptable results must be between 0.92 and 1.08 ppm at 25°C...

www.bulkreefsupply.com

If it turns out that you are running close to zero phosphate (remember there is a margin for error with the meter so a reading of 0.00 could be anything from 0.00 to 0.04 I believe) then I would remove the gfo and see if the phosphates start to come up.