How Many Glofish Are Actually Recommended Per Gallon?

First of all, let me point out that the “inch per gallon” rule does not apply to Glofish. Moreover, that rule is not and will never be correct for any species of fish. Imagine putting a 10-inch fish in a 20-inch (10 gallons) tank. With good filtration, It will probably survive, true, but will it be happy?