Using fish excrement is already a common practice when growing cannabis using aquaponics, but you can also use it even in non-aquaponic grows. However, the use of animal waste as fertilizer is nothing new, though it was usually extracted from land-based animals such as cows, chicken, sheep, pigs, horses, and others. The problem is that breaking down the manure from land-based animals is a lengthy process; for it to be used efficiently by plant growers – in this case cannabis, you want quality excrement that breaks down quickly so that your crops can feed on it.