i know you can buy a kit that tests for all but either nitrite or nitrate (forget which one) and this will run you anywhere from $13 to $20, depending on where you buy it (think its made by jungle but not sure, comes in a box and call "Freshwater Test Kit"). of course you'll have to buy a separte tester for the missing N, these usually run between $6 and $10, depending on brand and where buy. my one lfs overcharges for some, and undercharges on others. some of the online fish suppliers have them for less, but then when you add in shipping costs, it almost evens out. your best bet is to shop around a bit, either at online places or calling/going to you lfs and checking things out.