I use the Aquarium Pharmacuticals MAster Salt (ammonia, nitrite, nitrate, and pH), its a cheap and decent test kit.
Even though I like the aquarium pharmacuticals I dont think I will use it because I found out what some other people on here use (Salifert test kits). I was looking at some and they seem like good test kits and cover every basis you could think of, although they are a little expensive they look quite good.
I have used AP and thats been wonderful for FW, but I noticed that the ammonia test kit doesn't act the same, gets cloudy, so I'm thinking about trying one of those other ones for ammonia that is JUST for saltwater.
Eh...I didn't do it again yesterday, I'll try it again tonight. Just miffs me a bit that something is advertised to test accurately in salt and fresh...but obviously doesn't. I mean the color wasn't even close to the color chart. I might have to write AP on that one I need to mix up some fresh SW and test it and see if it gives me a true 0...cuz thats really all we're looking for right? Absence or presence...