[Delphinus]

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.