Backyard Aquaponics
A place to discuss aquaponics

There have been some questions on the forum about the accuracy of the different tests available to us to monitor water quality. There are two different styles, "strips" and "drops".

The easiest to use are the strips. They consist of a thin plastic strip with little square chemically treated pads on them. The strip is dipped into the water, the prescribed amount of time is waited (usually 30-60 seconds), and then the color of each pad is compared to a chart.

Slightly more involved are the drops. A test tube of water is drawn from the tank, the prescribed number of drops of solution are added, the prescribed time is waited (usually 0-5 minutes), and again, the color is compared to a chart.

But how accurate are they? Both Dave Donley and I thought we had noted that the strips gave low readings for pH. Hmmm...what else is inaccurate?

I have both strips (Mardel 5 in 1) and drops (Aquarium Pharaceutical Master Kit). I ran parallel tests on a tank that is almost done cycling up.

Mardel Strip:
ph 6.8
Nitrite 0.5 (Although the color for 1.0 is indistinguishable to me.)
Nitrate 20-40 (color was between chart colors)
Total Alkalinity 0-80 (color was between chart colors)
Total Hardness 250

Aq Pharm Drops:
pH 7.2 (double checked with Hi pH test which showed <=7.4)
Nitrite .25
Nitrate 10
Ammonia 0

I see serious discrepencies, but tend to believe the drop tests. The technology is more proven. Can anyone else perform parallel tests? It would be very interesting to see if the tests are really that far off.

Good thread, JP.

I only have the drops.

I'd tend to have more confidence in them as they use tritration (sp.?) of exact volume of reagents on exact volume of sample.

Those variances are really worrying! two of them were out by 50%

Yes, more parallel tests would be GREAT!

jp-good initiative. must be a few dual testers out there!

As I've already said in my own thread have serious doubts as to the accuracy of the particular strips that I use (JBL Easy Test 5 in 1). If there is anyone in Adelaide (particuarly the southern half) that uses drops and wants to get together please let me know.
The reason I chose the strips was 1. the man in the shop recommended them and 2. as a nurse we often test urine samples using strips and therefore assumed the pond tests would be accurate.
Thanks for starting a thread on this Janet

We are in the southern area of Adelaide and currently using Aquachek Select strips. As yet we are not advanced enough to have considered using a proper meter. (let alone the expense of one). Accuracy unknown, these are the strips that we used for our pool (no longer in use), something to do with lack of water...

We use drops in the indoor acquarium, although these only test ph. Once a month we take a sample to the nearest fish shop for full analysis.

After being ordered to post my results, here they are!
I cant tell any significant difference between my strips and my drops.
These are for my ph readings only as I do not doooo drops for nitrates
Using a 5-way test kit for swimming pools on the drops and a 6-way test kit for strips, Brand name hth.
My major problem with both is figuring out the color so I test and yep looks good or opps abit low or high, figure in my fudge factor and feed the fish.
All in all inconclusive results for me.
Inconclusive is my word of the day.

Thanks GF!

A yep. ....grin....

I finally got to test my strips against the Master Test Kit today (thanks to Peterall for bringing his down)

Test strips
pH 6.2
nitrite 25
nitrate 100 (or somewhere between 50-100?)

Master Kit
pH 6.7
nitrite .25
nitrate 40

I havent tested the water for a long time now so in one respect it doesn't matter much, but I have a sneaking suspicion that the Master Kit is more accurate and I wouldn't buy the strips again.

That's a huge difference in "nitrites" KE.... or did you leave out a decimal point in the "strip" result?

I think it's just a missing decimal point. If his nitrites really were 25, the fish would be floating.

The difference in pH is what catches my eye. At 6.2, I'd be trying to raise it, but at 6.7, I'd just let it ride.

True, true.... big difference in the nitrates between the two as well.

the method of testing using reagents with the drops is far better then the strips.

I thought the master kit nitrate reading looked bit higher than 40, but I might be wrong...

I have trouble reading the test results at 40+. Dilute the water sample 50% with distilled water or other water known to have 0 nitrate. Multiply the result by 2 to get your true reading. Use different dilution rates as needed to get a color you can read.