Question: how much gfo should i use?
Answer: start with 1 tablespoon per 4 gallons of water (16 tbsp = 1 cup). After 4-8 weeks the aquarium will have adjusted to lower nutrient levels and the amount of GFO can be increased up to 2 tablespoons per 4 gallons of water. For HC GFO start with 1 tablespoon per 8 gallons of water (16 tbsp = 1 cup).