I recommend two different brands of "good" test kits. That way you can compare results and ensure a good outcome. Avoid cheap test kits, as they tend to be less accurate. Even by just looking at the instructions and ranges on result sheets, you can get a pretty good idea of how accurate they are. Salifert and seachem are pretty good, but in all honesty, if you don't have a reef, it would be too much time and money to invest. Aquarium Pharmaceuticals isn't very good. If you have a Fish only tank and are on a budget, I think hagen is a pretty good choice. But nothing IMO beats Salifert.