Api Master Test Kit Vs. Tetra Pond Water Test Set

[joilet]

Hi

I have two water test kits that both test for ammonia, yet both produce very different results.

Tetra Pond Water Test Set

This was my original water testing kit that i bought when i was doing a fish-in cycle. This was the only liquid based kit my LFS had in stock at the time.

The ammonia test consists of 3 bottles of liquid that must be added to 5ml of water.

Instructions

1. Clean test vial by rinsing it with water to be tested
2. Fill test vial until water curve even with 5ml line
3. Add 14 drops of reagent bottle #1 cap and shake well
4. Add 7 drops of bottle #2 cap and shake well
5. Add 7 drops of bottle #3 cap and shake well
6. Wait 20 minutes till comparing against colour chart

Result: 1.5 mg/l

API Freshwater Master Test Kit

The other tetra pond kit didn't test for nitrates. I ordered the API kit approximately 4 weeks later.

Ammonia test consists of 2 bottles. Batch numbers (last 4 digits) range from 1210 - 0311. Providing these represent MM/YY then the kit was produced recently.

Instructions

1. Fill clean test tube with 5ml water
2. Add 8 drops from ammonia test solution bottle #1
3. Add 8 drops from ammonia test solution bottle #2
4. Cap test tube and shake vigorously for 5 seconds
5. Wait 5 minutes before comparing against colour chart

Result: 0 ppm

Why do both tests produce such different readings... I immediately realised the tests use different units of measurement: ppm & mg/L. A quick look online suggests there is no differnce, however looking at it in further details reveals mg/l to be relative to the volume and weight of the water. Pure water generally has a density of 1kg/L which would support that there is no real difference between the two unit types. This only seems to be true for solid mediums.

Both kits report Nitrite at 0 and the API kit reports Nitrate at 20 ppm which suggests i'm cycled. My water is crystal clear and it hardly produced an odour. Plus my fish are much better looking now than they were at the beginning of my fish-in cycle. Initially i kept suffering cloudy water, then this progressed to an algae bloom. It also smelled absolutely rank! I can only assume that the Tetra pond kit is inaccurate, at least the ammonia test is anyway. Interestingly the test seems to use an additional solution as it requires solution added from 3 bottles and not 2 used by the API master kit.

Anyone have any thoughts on this? Thanks

 

[Peggers]

The temperature of the water is important. The tetratest one I have says the water must be between 20 and 30C so maybe the pond one needs colder water.

 

[@ombomb]

how old is the original test kit? they can often degrade over time

personally i always used the API kits for freshwater with no problems

one thing which suggests to me that the API kit is the more accurate is the lack of nitrite and presence of nitrate. if you are seeing nitrates then clearly you have a cycled or mostly cycled tank, keep an eye on the nitrite levels over the next 24 hours, if you don't see a nitrite spike and the ammonia reading stays the same, i think it's safe to say that the tetra reading is a false positive