Different results from two test kits

Hi folks.

In February we bough a 190 litre tank. It has some live plants in it.
We currently have

6 neon tetra
2 serpae tetra (was 6)
2 Pimelodus pictus
1 three spot gourami
1 pearl gourami
1 opaline gourami

The tank was cycled for two weeks. I had the water tested by the fish store before adding the neons. We have since slowly added more fish to the tank.
The only problems we've had is with the serpaes. So far we have lost 4 of them. The last one had what looked like pop eye. The rest of the fish seem happy out.
Up until today I had been using a Nutrafin test kit to keep an eye on the parameters. Today I used an API test kit and the results are different.

The Nutrafin kit has been showing the following:

pH: 7.0
Ammonia: 0
Nitrate: 0
Nitrite: 0

The API kit is showing:

pH: 7.6
High range pH: 8.0
Ammonia: 0.50
Nitrite: 0
Nitrate: 5.0

Now I have since learned that I probably didn't let the tank cycle long enough. However I'm a bit confused in the difference between the two test kits. Which one is giving the correct measurements? If the API is more accurate what do I need to do to reduce the ammonia? I currently do a 20% water change on a weekly basis.
Could the high pH be causing problems for the Serpae?

If pH were a problem for the serpae, then you would also be having problems with most of the other fish.

No aquatic test kit is 100% accurate.....each may use different reagents,
may have different sensitivities,
or be prone to interference from differing other chemicals in the water.
Some tests kits would be more prone to user error than others....no matter how carefully you follow the instructions.
ie there are a number of reasons why 2 test kits give differing results.

I assume that the tests were all done at the same temperature......that is very important.

pH can also change quite rapidly in an un-buffered tank. So even a few hours could mean a difference.

The main concern would be the level of ammonia measured....if 0.5mg/l is correct then that is dangerously high even if it is only ammonium (as that would easily change to ammonia at higher temps and increasing pH).

It may have even detected the ammonia from chloramine if you use certain dechlorinating agents.

I wouldn't worry too much about the nitrate level....it is too low to be of concern.

SO.....all in all that begs a question on using test kits:
do we go for absolute accuracy? or
do we go for precision?

absolute accuracy is very difficult to obtain, and would need on-the-spot standardisation on every single test you did. That would require chemistry lab equipment, and is not really needed in my opinion.

So...go for precision instead. ie the test kit itself is the benchmark, and you compare results taken with the same kit to see changes and trends. Know your test kit and get use to its readings.

As for which of the 2 kits are best or most accurate?.....I wouldn't have the faintest as I've never used those brands.

ian

Thanks Ian.

The tests are done at the same temperature. The ammonia reading was 0.50 ppm and not mg/l.
I lost another serpae today so now down to just the one.
I've done a water change this evening. I'll keep an eye on the parameters over the next few days. Going to use the API kit. After reading some reviews it seems to be quite good.

Hi nephin,
listen i've had and i am having similar problems to your self so i will pass on the advice i was given here....... Do not put any more fish in your tank until your ammonia,nitrite and nitrate readings are a big fat ZERO....Do 10/15% water changes daily but do your testing before the water change!!

Now with your ammonia at 0.50 ppm this could be the reason for the serpae deaths but why are your other fish not having problems,hmmm..thats not one i can answer sorry!!

You were wondering if the PH could be a factor in your deaths but the neons ideally need a lower PH than the Serpaes so i doubt if thats the reason!

Anyway,from one rookie to another,all the best dude and post how your getting on

Ger

Nephin wrote:

Thanks Ian.

The tests are done at the same temperature. The ammonia reading was 0.50 ppm and not mg/l.
I lost another serpae today so now down to just the one.
I've done a water change this evening. I'll keep an eye on the parameters over the next few days. Going to use the API kit. After reading some reviews it seems to be quite good.

Nephin.....ppm is a w/w measure in the test kits, and as we are dealing with water then ppm = mg/l. So 0.5ppm = 0.5mg/l (the test results would not be sufficiently accurate for us to make allowances for the marginally slight differences in water density at differences experienced).
I, normally, however do not like using ppm nor mg/l I prefer moles per kilogram or moles per cubic decimeter as they are actually more related to the important values experineced by the fish.

The serpae deaths? the lace gourami (pearl gourami) would demand a more strict acid pH for proper health.
The serpae could be simply a problem with the batch.....or they may have been poisoned by certain compounds in the water, or by certain toxins produced from bacteria or fungi (eg eating go off food found in some corner of the tank maybe).

ian

igmillichip wrote:

Nephin wrote:

Thanks Ian.

The tests are done at the same temperature. The ammonia reading was 0.50 ppm and not mg/l.
I lost another serpae today so now down to just the one.
I've done a water change this evening. I'll keep an eye on the parameters over the next few days. Going to use the API kit. After reading some reviews it seems to be quite good.

Nephin.....ppm is a w/w measure in the test kits, and as we are dealing with water then ppm = mg/l. So 0.5ppm = 0.5mg/l (the test results would not be sufficiently accurate for us to make allowances for the marginally slight differences in water density at differences experienced).
I, normally, however do not like using ppm nor mg/l I prefer moles per kilogram or moles per cubic decimeter as they are actually more related to the important values experineced by the fish.

The serpae deaths? the lace gourami (pearl gourami) would demand a more strict acid pH for proper health.
The serpae could be simply a problem with the batch.....or they may have been poisoned by certain compounds in the water, or by certain toxins produced from bacteria or fungi (eg eating go off food found in some corner of the tank maybe).

ian

Thanks Ian. I'm still a novice so didn't realise 0.5ppm = 0.5mg/l. I hope you didn't think I was doubting your advice

My initial thoughts regarding the serpaes is that there was a problem with the batch. The rest of the fish seem healthy and happy. Hopefully this will continue.

Nephin wrote:

Thanks Ian. I'm still a novice so didn't realise 0.5ppm = 0.5mg/l. I hope you didn't think I was doubting your advice

My initial thoughts regarding the serpaes is that there was a problem with the batch. The rest of the fish seem healthy and happy. Hopefully this will continue.

Not at all.
the units are all quite important, and the problem of ppm is that it is ambiguous in any sense in the wider world outside of fish-keeping. A ppm result could be giving a value of ppm as a weight-by-weight value, or ppm as a weight-by-volume value, or ppm as volume-by-volume.

Environmental scientists like to use one type of unit, chemists and biochemists prefer to use a different set of units.

On the serpaes……they could have acute or chronic toxicological symptoms due to their original source (eg pesticides in the area), their transport, or even something in your tank eg medication.
Not every toxic substance kills instantly….and even ammonia has long-term effects when a fish is exposed to sub-lethal levels.

There could be a lot speculation as to why a batch dropped off…..maybe their diet was not upto scratch before being transported (eg not enough anit-oxidants such as carotenoids) and they were unable to protect themselves against the stress induced by sub-lethal levels of ammonia in the bag…..the effect would be a delayed death.
And…the list could go on.

Ian