As a rough guide, for my adult fish (and these are full sized adults about 30cm long) I give them about a teaspoon of pellets, or two or three algae wafers, or.
How Often Do You Feed Fish? Most fish are fine with being fed once a day, but you can also choose to feed them two smaller meals a day for more enjoyment.
The old saying is 'weekly, weakly' but usually I aim for fortnightly to every three weeks. Diluted liquid or slow release fertiliser. Depending on variety.