There has been allot of post about test kits. I have to admit that I have as much trouble with them as any one. Here is two SeaChem kits. PO4 and NO3. I like these kits because I can test several tanks at one time, BUT they give me trouble all the time. I don't think I have ever had the PO4 kit give me a color that ever match any thing on there chart. The NO3 test seem to more accurate. If anyone can match the color of the PO4 to he color chart let me know. I just don't see it. As far as the NO3 I see Tanks 1, 2, and 3 at less than 5. Tank 4 looks very high all most 40.

Because of all the trouble reading the SeaChem test I thought I would double check with a different brand kit. I've been using the Hagen on and off for a while with good results so I finally broke down and sent the bucks for the Deluxe Kit. Using the PO4 and NO3 test to compare to the SeaChem.

PO4 tests with Hagen show tanks 1,2, and 3 at or less then .25 and tank 4 is .5. The color in the Hagen kits are so faint I couldn't get a good picture to post so I will just tell you the readings. SO am I to think that the SeaChem PO4 doesn't give actuate reading in low levels of PO4? Could this be why the false color with their test? I thought that the color in the SeaChem test where reading very high levels of PO4 so I tried to up my NO3 to get the tanks back to the 1/10 ratio of PO4/NO3. By doing so I have small out breaks of algae. On one tank I had a major out break but there where other things at the time that contribute to the problem. Tank 4 with the Hagen show the PO4 to be right in where I want it .5 but with the SeaChem I thought it was extremely high. I tried water changes to try and bring it down but I never changed the results of the SeaChem tests.

NO3 tests with the SeaChem and Hagen seem to be close to each other. All thou I would say the SeaChem reading are Closer to 2 and the Hagen is closer to 5. On tank 4 with the Hagen test it is a solid 5 the SeaChem shows much higher levels.

So what to conclude? Wouldn't it be nice if you could use a test kit and then dose ferts to maintain your target levels, but its not the case. Test kits are only reliable if we can interpret the results correctly. A lot of experienced plant aquarium enthusiast have learned not to rely on test kits. By watching their plant growth, leaf color, old and new they can tell you allot about what plants need for healthy growth. I'll keep using them but I will not rely on them as strongly as I have in the past. As a beginner I would test at lest once/week most of the time. Getting burned on bad kits and not reading the color charts correctly I think Its time for me to start listening to tmy plants. I have been in full learning mode on plant aquariums going on five years now. Its time to grow in my knowledge and stop falling into the false dependence on test kits.

I hope to here about some of the experiences you have had with test kits as a beginner or a more experienced plant enthusiast. I think if we talk about our experiences we can help others.

update 2/1/05
post by Roger Miller:
Regarding PO4 kits...

Phosphate is a difficult test. The biggest problem for me is that silica interferes with the test. My tap water carries quite a bit of silica. Usually this the interference causes a false positive. The color produced when silica is present is also a little more blue than it is supposed to be.

Over the years I've tried most of the phosphate kits I've found available locally. None of them work quite right. The worst was a dry-tab test in which the tabs didn't dissolved. They produced a fluffy white floc instead, and no color. The company replaced my first kit, but the second one acted the same way.

I was moaning about phosphate tests to Greg Morin and Doug Hill (Seachem) at one of the AGA conferences and they sent me one of the Seachem kits to try out. Following the kit instructions the test solutions were murky and the colors did not match the test strip. I also had the problem that the kit instructions wanted me to make the color match 30 seconds after mixing the reagents. After about 30 seconds the color changed. That isn't enough time for me to do a color match.

After fumbling around with the kit for a while I found that I could add the reagents in the reverse order (#2 first and #1 second) then wait 6-10 minutes before reading the color chart and I got better results. I read into the basic test method and found that the standard method required a 10 minute wait to allow colors to develop. I discussed all that with the good folks at Seachem and they told me that their instructions were set up to avoid having people wait 10 minutes for a result. They were afraid that a wait would make the kit uncompetitive in the market. Otherwise, #2 first and #1 second is the standard method for the test.

Anyway, I used up the kit. At first the results were very good -- I'd say the best of any hobby-level PO4 kit I've used. The last few tests didn't seem to work right, producing colors that were too blue to match the chart. I don't know if the water changed or the reagents aged.

That was a couple years ago. Has Seachem changed their kit instructions since then?

On the topic of kit accuracy more generally, the hobby kits are made to give retailable results at the lowest possible price per test and with minimum inconvenience. I don't think accuracy is even on the list of standards for a hobby level kit. If you want accuracy (not just pretty colors to compare to) then you should spring for the more expensive Hach or LaMotte kits. If you consider the consequences of mis-managing a large tank because of an inaccurate test then it makes the higher cost seem more reasonable.

Roger Miller

update 2/27/05
Its a endless frustration for beginners on a beget. All we can hope for is prices to come down on the really good test kits.

Hawk