When it is filled with cut-feathers. Tetra Test 6 in 1 Water Quality Test Paper (Free Research Instructions) Target Freshwater Features; Water Quality Measuring Paper "Tetra Test 6 in 1" for Aquarium Water Quality Inspection Guide and Set for Free Research. The measurement methods are very easy by soaking water on the paper (6 in 1), so you can test it in one day if you do hard. If you use it with accessories that change the water quality (such as kulki), such as kulki remover can further deepen the experiments, so you can use it for free research. Set Contents: Tetra Test 6 in 1 Water Quality Test Paper (for Freshwater) 25 sheets per pack Simple Instruction Manual (English language not guaranteed) Free Research Water Quality Inspection Method (Inspection Water Quality) pH (PAH), KH (Carbonate Hardness), GH (Total Hardness), NO2 (Nitrititate), Cl2 (Chlorine) Experiment Method ● Small Plate or 6 1 x in1 Place it on and drip the water to be investigated above it. (1 piece can be found on the top of 6 items. ) Record the value by matching the color of the paper with the included checker.