Very accurate, but $$$, I have 1 for NO3, Its served me well.
Jeffww, I dont understand what you are saying?
The accuracy that these kits provide goes beyond our uses. We will never need to know any information beyond the fact that:
1. Nitrates have not bottomed out and are not beyond safe or acceptable levels
2. The pH is relatively stable is within an acceptable range
3. Ammonia is not present in the system in any measureable way.
4. In general parameters are not "out of whack"
In other terms we don't need to know anything more what the cheap API kits can tell us. Purchasing a highly accurate kit is only so useful to us since we can't ourselves affect water quality except in a very global/broad/guesstimative perspective with regards to our tanks. Additionally knowing the measurements of parameters to a +- 5ppm isn't really necessary for growing good plants and keeping healthy fish.
Save that cash and buy more plants + fertilizer. You'll need it more than having an at home lab. (however appealing that may sound to me)