The Hanna phosphate checker is a green, egg-shaped hand-held colorimeter for portable testing of phosphate concentration with digital precision. If you’re like us, you’ve probably been wondering how Hanna could make such a small and affordable little colorimeter that could even begin to stack up to the accuracy of larger colorimeters from Hanna and others which cost ten to twenty times more than the $40-50 checker. Hanna was kind enough to send us a review unit of the little colorimeter for stacking up against our workhorse Hanna C 203 Multiparameter Ion Specific Meter. Over the last week we have performed dozens of tests where each reacted sample was read both by the Hanna Checker and Hanna c203. In every case the Checker was well in line with the readings of the C203 although some drawbacks of the checker became apparent when it was put to regular use. Continue reading to find out how the Hanna Checker still delivers on good value that will make it a worthy tool for precise measurement of phosphate in reef aquaria.
The Hanna checker is very easy to use. Turn it on, insert an unreacted sample of water to get a zero baseline, then add a reacted sample and take a measurement. Such simple steps are impeded by the fact that the green egg colorimeter likes to turn off every 10 seconds. We suppose this is to preserve battery life but there is no way to reopen the cuvette, carefully add the reagent and shake/invert it for 20 seconds, and reinsert the cuvette in under ten seconds. Furthermore, by holding down the only button you can set the timer to take a reading in 3 minutes, the length of time that the sample needs to be reacted for. Finally, after the three minutes are up the reading is displayed for only ten seconds after which it shuts off, and is not displayed once the unit is turned back on again. Ten seconds may seem like long enough but take a phone call, get distracted by a text message or bend over to tie your shoe and your sample has been colorimetered, displayed and erased and you’re out the 5 minutes and the roughly $0.25 it costs per reagent packet. However, since the egg-orimeter ships with two vials, we quickly developed a workaround which largely addresses the flash reading: one cuvette is filled with unreacted sample and the second cuvette is reacted and timed outside the sequence of the egg-orimeter.
Compared to the larger C203, the Hanna Checker / Egg-orimeter gave phosphate readings from the same reacted samples which we were almost always identical in the low range and only slightly off at higher concentrations. For our freshwater planted tank, tap water and RO water all readings were 0mg/l. One reef tank was 0.02mg/l and 0.03mg/l from the egg-orimeter vs the C203 and for a fish only aquarium the level was 2.20 and 2.25mg/l from the two units respectively. We made a phosphate reference solution using 0.3l of Seachem’s Flourish Phosphorus (4500 mg/l) additive for planted aquaria to 999.7 ml of RO/DI water for an expected PO4 concentration of 1.35 mg/l. Both the Hanna Checker and Hanna C 203 gave readings of 1.31mg/l when testing this solution. One final note is that the Hanna Checker was significantly faster at zeroing and taking readings than the tabletop C203; whereas the egg-orimeter usually did it’s measurements in 2-3 seconds, for the C203 it usually takes 10 seconds to read a sample.
It will be a long time before long term performance of the egg-orimeter becomes better understood but for now, we feel the $40 hanna phosphate checker will be very popular with aquarists who obsess over nutrient levels of their SPS tanks and for aquarium professionals who need a practical, portable device for delivering accurate, digitally precise phosphate testing.