A website that sells Eco-complete said that you should go 1 pound per gallon of water. So 3 should cover it, but another said one bag per 10-20 gallons. If you go with the one bag for 10g then 5 bags for a 55 or if you go 20g then 3. And then there are a few people that say 2 inches on the bottom, well, how much does it take to get 2 inches?