I recently posted a message about how many fish you can have in a 20 gallon tank. I later found out that my tank actually holds around 25 uk gallons. In my tank i had a pleco (around 7 inches), 4 angels, 2 gourami, 6 glowlights, 5 guppy's, ruby shark (very small at the mo) and a tank cleaning cory. You told me that my tank was over crowded and so i have given my Pleco and an angel to my local fish shop. Can you advise me on how many water changes i need to do, currently i do it weekly.