I thought a quarter teaspoon was supposed to treat like 300 gallons.
That depends entirely on your local tap water disinfectant residual. It also depends whether you have chlorine treated tap water, or chloramine treated tap water. See below ....
Directions for 10 g and 50 g
To remove
Chlorine: use 1 measure to each 130 L (35 gallons*) of tap water (removes 1 ppm)..
Chloramine: use 1 measure to each 100 L (25 gallons*) of tap water (removes 1 ppm).
Ammonia: use 1 measure to each 32 L (8 gallons*) of tap water (removes 1 ppm). Do not overdose!*
For reference, 1 measure = 100 mg. To detoxify nitrite/nitrate in an emergency situation use up to 5 measures to each 40 L (10 gallons). Use fish to gauge toxicity reduction as test kits will still show presence of nitrite/nitrate even when detoxified. May be added to
aquarium directly, but is better if added to new water first. If adding directly to aquarium, base dose on
aquarium volume. If temperature is > 30 C (86 F) cut dosing in half.
Directions for 250 g and larger
To remove
Chlorine: use 5 g (1 tsp.*) to each 1625 L (450 gallons*) of tap water (removes 4 ppm).
Chloramine: use 5 g (1 tsp.*) to each 1250 L (300 gallons*) of tap water (removes 4 ppm).
Ammonia: use 5 g (1 tsp.*) to each 400 L (100 gallons*) of tap water (removes 4 ppm). Do not overdose!
