phosphate testing
 

What is the best one?

Hanna Photometer.

http://www.jlaquatics.com/product/hn...hotometer.html

My vote is for the Merck Phosphate test kit. Pricey but works like a charm.

http://oceanaquatics.com/store/produ...hate-Test-Kit/

The Merck test kit works very well, especially for detecting low levels of phosphate. However the refills cost too much.

Has anyone checked out the Elos test kits?

The Elos PO4 test kit is easy to use, like most Elos test kits, but not very good at low range numbers (like most PO4 test kits).

I tried the Hanna photometer and disliked it. Could not get a steady reading. I tried new reagents, I tried other photometers and it was always the same story. 0.00, 0.10, 0.02, 0.04, 0.16 ... etc. .. It was all over the place. I would have had better accuracy just by waving my hand over the test sample and then stating the first random number that came into my head. I can do that without spending $160.

The Merck/D-D test kit is pricey but has a good low range and most importantly I *get the same results, test after test*. It can tell you down to 0.000 to 0.008 which the Hanna photometer can't even go down to (0.00 or 0.01 is all it would tell you, if you can ever get the #'s to read the same twice in a row). So my opinion is that the Merck/D-D is the only one worth its price.

My advice after 2 years of convincing myself that test kit after test kit must be faulty because they would either tell me zero (or random numbers like in the case of the Hanna) .... is that PO4 testing is overrated. I don't know. I feed pretty heavy and I can not get a PO4 reading. NO3 out the wazoo. If you have high PO4 then I think something's off. My $0.02 anyhow.

The main use of my Merck phosphate test kit was for a one-time reading to assure myself that my phosphates weren't high.

I also use it for my FW plant tanks.

Some people don't think that zero phosphate is actually a good thing. Some Zeovit users are actually dosing small amounts of phosphate in order to keep some color in specific species.

I'm starting to think phosphate testing is overrated.I have a merk kit and its always at 0.Yet i still get algae.I think nitrates may be better to keep in control.

I think the phosphates get immediately (or pretty darn close) tied up in the growth of algae. SInce the alge is harbouring them, theres none to be measured. I have close to zero phosphates and have caulerpa glueing all my rocks together. I have to "harvest" it monthly from one of my birdsnest corals.

I just got a Hanna HI 93713 Phosphate low range photometer and I am confused by the readings I got from it.

For my reef tank I got 1.82mg/L.
For my FOWLR I got 2.70mg/L.
WTF? My PO4 has never been above 1.00. My FOWLR tested at that for a time in ’06.

The powder was not completely dissolved when I put the sample in the photometer. They say to shake it gently. But they also say to time it for 3 minutes once the sample is in the photometer. But I’m assuming time is of the essence, given the 3 minutes timeframe? I can’t be standing there shaking the sample hard for 10 minutes until the powder is dissolved, can I? They say not to let it stand for too long. They say nothing of ensuring the powder is fully dissolved. But they do talk about debris and bubbles throwing the reading off.
Oy vey! Yet another test kit with crappy instructions.

The leaflet says it measures PO4³ˉ. I see on Wikipedia that that’s inorganic phosphate. Okay.

The leaflet has conversions. To convert PO4³ˉ to P2O5 multiply reading by 1.49.
To convert PO4³ˉ to P multiply reading by 0.33.

I have been using the Elos PO4 kit for testing up to now. I should state that I do not read this test exactly as directed by Elos. They say to look down at the sample through the top of the vial. I have always looked from the side, as this is how other test kits are.

Latest readings with Elos was yesterday.
Reef: < 0.1
FOWLR: 0.1

If I convert my Hanna readings to P, I get.
Reef: 1.82 x .33 = 0.6006 mg/L. This is more like it!
FOWLR: 2.7 x .33 = 0.891. Again, more like it!

I don’t get what I’m missing here.

I’m assuming P is organic phosphate? Maybe I should just be happy with the converted readings I get of that? I have read/heard that organic phosphate is the more important phosphate to keep tabs on anyway?

Sorry. This chemistry business is one of my weaker aspects of the hobby.

Anyone with any experience or light that could be shed on this would be greatly appreciated.

Thanx much,