Making sense of Phosphate readings

[asylumdown]

So after a massive campaign of water changes to try and save my tank, I'm at the point where I'm starting to add some of the reactors and dosing equipment that I took offline back to my system.

The first thing that I added back was my GFO reactor, filled with rowaphos, as I'm finished doing massive water changes every day and I presently have zero nutrient control on the tank.

Using the Hanna ULR kit, 2 days ago I measured P levels of of 29ppb, which when you do the math works out to 0.088ppm PO4, which is higher than I normally like my tank to run at. Right after that I added the GFO reactor back to the system and filled it with Rowaphos. Frustratingly, the next day the ULR kit measured P of 36ppb (0.11ppm PO4) and today it measured 46ppb (0.14ppm PO4).

Is this just my test sucking? How is it possible that my phosphate levels are rising after adding an adsorber? Do I need to put way more Rowaphos in the reactor?

My nitrates have also been steadily increasing since I took the biopellets offline as well. Even with a 60% water change earlier in the week, and 10 20% water changes in the days around that big change, my nitrates have climbed to 1ppm from undetectable. grrrr.

[jordsyke]

I find that in my 45 gallon tank I have the same issues, I beleive that over the years the sand has just grabbed so much crap that it is forever leaching back into my system.... In my 120Gallon I use both biopellets and GFO and find a can easily keep my nitrates at 1ppm which is fine to me, and .06-.15 phosphates which is also an acceptable level in my mind

[asylumdown]

well what's weird is that I've always run GFO and have had very low phosphate for the entire life of the tank. However, I haven't had the ULR test kit for very long, I was using the regular hannah checker which would routinely show me having no phosphate. But now with the ULR kit, I'm not sure if my results are 'real' or if they're the natural variation in responses I'd get from not doing the test exactly the same each time.

[MarkoD]

I have been running zeo for 3 weeks and my phosphates are at .35ppm as per the Hanna checker

[mark]

simple as the Hanna testers are, drift you're seeing could be just errors in testing

[Magickiwi]

Originally Posted by mark

simple as the Hanna testers are, drift you're seeing could be just errors in testing

+1 I think those are pretty good #'s for Hanna testers. They are only advertised +/-5% accurate and I would be very surprised if they are really that accurate.

[Wheelman76]

Originally Posted by Magickiwi

+1 I think those are pretty good #'s for Hanna testers. They are only advertised +/-5% accurate and I would be very surprised if they are really that accurate.

Who knows how accurate the checkers really are , however keep in mind that the regular checker is +\-5% ppm , whereas the ultra low range phosphorous checker is +\-5% ppb which is more accurate.

[Myka]

I think people rely a bit too heavily on nitrate and phosphate test results. I think we have a tendency to try to measure and control as many variables as possible, and in this blinding determination we fail to really look at the tank.

You say you filled up the reactor - exactly how much RowaPhos did you use? RowaPhos is quite aggressive. In my experience, too much GFO is much more detrimental than too little (or none). I hope you are adding your equipment back cautiously and "gently".

[Wheelman76]

Completely agree ^^

[asylumdown]

Normally I don't pay much head to nitrate and phosphate tests, and I normally only test the major ions once every couple of weeks. I'm paying extra special attention right now because things were so unbelievably out of whack, and then I took everything offline, so I'm doing all this testing to get things back on track. Once all my systems are back in place and my auto-dower is dialled in I'll probably go back to hardly ever testing.

And I'm going to stop trusting my hanna checker. With the rowaphos in there (and I used about 15-20% of the amount I would normally have put in if it was just regular bulk GFO), I was seeing a steady climb every day. I changed out the Rowaphos last night because I thought that maybe with such a small amount in the reactor it had honestly already been exhausted, but this morning it measured 0.21 after the conversion to PPM Phosphate, which shouldn't be possible unless the Roawphos was actually contributing phos rather than removing it. I've been using the same glass vial for each test though, and right after I got the 0.21 result, I swapped out the vial for one of the vials from my calcium kit and got a result of 0.008ppm phosphate.

I think my vial has been getting imperceptibly stained by each sequential test. I gave it a thorough wash with a bottle brush cleaner and laboratory soap two days ago, and I empty and rinse the vials with distilled water immediately after each test, but it's apparently not enough. I don't know how else to clean it, and it looks spotless to my eyes, but when one vial gives you 0.21ppm and another vial gives you 0.008 with the same water following the exact same protocol, it makes me not trust any of the results if the equipment alone can contribute such a wide margin of error.

As for the nitrate tests, today it was 2ppm. It's been a clear and steady increase since I took the pellet reactor offline and stopped doing massive daily water changes. More than anything I think it's just interesting to see, as my tank has never not had pellets on it so I really had no idea what it would do without them. I don't necessarily trust the numbers exactly, but I do trust the relative colour development which indicates that my nitrates are definitely rising. The Red Sea nitrate kit uses the same reagent protocol as my faculty's analytical hydrogeology lab (which really means it shouldn't be going down the sink as there's cadmium in it, but Red Sea doesn't tell you that), and while my lab would use a Hach spectrophotometer to measure the colour exactly, you can get a really good qualitative idea of the amount of nitrate in the sample just by looking at how red/pink it turns. And every day since wednesday my sample has been progressively pinker than the day before.