Which test kits do you use?

Just on Nitrates alone I got a ready of >160 ppm with a API kit, slightly lower with a Seachem and 30 ppm with a Salifert.

On Nitrites I got a reading off the scale with API, which turned green after 5 minutes, also not on the scale. Salifert gave me a reading of .5 ppm.

These readings were on tanks that I was cycling.

A friend of mine got a reading of Nitrites with a API test kit, again off the scale, on a occupied tank.

I am not impressed with these test kits. The swings in their results are useless.