If you own a saltwater aquarium, you know how important it is to keep the water within the proper parameters. Aquarium Pharmaceuticals has a Saltwater Master Liquid testing kit which is very accurate in checking your water. It takes a little bit of time in order to use this kit, because you have to measure out a certain amount of water from your tank in a test tube (makes you feel like a scientist), then you must put a certain number of the proper liquid drops into the test tube and shake the tube, wait the required amount of time, and check the color of the liquid against a chart to see if your water is healthy. That is the disadvantage of this kit, it takes time. But it is extremely accurate, and once you get the hang of it, it really is very simple to do.
The Saltwater Master Liquid Test Kit has liquids to check for high range pH, ammonia, nitrite, and nitrate. With this kit, you can keep a close eye on the quality of the water in your aquarium, so that if problems in the readings should occur, you can catch it in ample time to correct the problem and save your fish.
There is also a kit for freshwater tanks (which I also have). Each kit contains an instruction booklet for testing the water, color charts which are water resistant, test solution bottles to enable you to do 4 different tests, and 4 glass test tubes with snap-on caps.
If you have saltwater tanks and want to be certain that the water is within the proper range, this is the kit that will enable you to do that.