Electronic device:
- pH
I also check it with other products from time to time just to avoid false readings.
Salifert:
- Alkalinity
- Calcium
- Magnesium
These are very easy to use and very precise. I also ordered Red Sea Alk/Ca/Mag and I'll see if there is consistency between them.
Red Sea:
- Nitrates
- Phosphates
The Nitrates test is great, but nothing beats their PO4 test, it's so easy to read! The overal quality of the kit is awesome.
Nyos:
- Nitrates
This test kit is very good, easy to use and of great quality. But hard to find around here.
Seachem:
- Ammonia
Mostly because it can read toxic Ammonia AND total Ammonia. And it's so easy to use. Their pH/Alk test is a joke though, I could never make it work.
Notes:
So far I haven't found any reliable test for Nitrites, but since we always aim at 0, most of the test will do.
I've also tried Hanna (I have most of them), I'm not happy, you can easily leave it for few more minutes while doing something and they turn off and erase the reading. It's quite frustrating, considering the prices of the refills.
For fast measures: Tropic Marine Alkalinity, since it has easy double dose (10ml water) that gives 0.5 dKH measurement that I find consistent with the Salifert test.