API aquarium test kits are an amazing buy for the money.  Fairly accurate and cheap are things not often found in the hobby. 

Aquarium Pharmaceuticals (API) Reef Master Test Kit   API aka Aquarium Pharmaceuticals is known for cheap and accurate test kits.  They are great for even the expert aquarist. Kits and descriptions: Master...

Aquarium Pharmaceuticals (API) Saltwater Liquid Master Test Kit   A complete kit for testing marine aquarium water. Tests water four ways to protect marine fish and invertebrates from dangerous water conditions. Kit...

Aquarium Pharmaceuticals (API) Ammonia Test Kit Salicylate test measures ammonia levels in both fresh & saltwater aquariums. Ammonia, the #1 killer of tropical fish, is continually produced in the aquarium from fish...

Aquarium Pharmaceuticals (API) PH High Range Test Kit Use to measure pH changes in marine aquariums, aquariums with African cichlids, and very alkaline tap water. Reads the pH of water within the high range of 7.4 to 8.8...

Aquarium Pharmaceuticals (API) Calcium Test Kit This kit allows for easy and accurate measuring of calcium levels to help in maintaining a healthy aquarium.Why test for Calcium?Monitoring calcium levels is essential for...

Aquarium Pharmaceuticals (API) Nitrate Test Kit Measures nitrate levels in both fresh & saltwater aquariums. Tests nitrate levels from 0 to 160 ppm. 90 tests per kit.Freshwater/Saltwater Nitrate Test Instructions:Why...

Aquarium Pharmaceuticals (API) KH Carbonate Hardness Test Kit Tests tap water & fresh or saltwater aquariums for carbonate hardness (KH). Helps prevent fish stress caused by rapid pH shifts, the result of low levels...

Aquarium Pharmaceuticals (API) Phosphate PO4 Test Kit Test reads 0 to 10 mg/ or parts per million (ppm) of phosphate. Helps to decrease the likelyhood og having unsightly algae and green water blooms.Test kit of 150 tests...

Test reads 0 to 4 mg/L or parts per million (ppm) of copper. Helps to maintain a healthy aquarium or pond for fish by ensuring that copper (a common treatment for many parisitic infections) levels are within the healthy...

Aquarium Pharmaceuticals (API) Nitrite Test Kit Tests for nitrite in freshwater & saltwater aquariums. Toxic nitrite is produced by nitrifying bacteria in the biological filter as it breaks down ammonia. This kit...