We all have that customer who loves fish and collects them to the point of overcrowding their pond. While fish certainly bring joy to any pond, they can also bring headaches to water quality if your customer goes overboard when stocking fish. Too many fish creates an imbalance in the pond's ecosystem so you'll want to make sure your customers are smart about the number and size of fish in their water garden.
Obviously, the pond needs to be large enough to support fish and their growth. Pond fish generally need 10 gallons of water for every inch of their length, and your customers have to be ready for them to grow larger, so they should be careful not to overstock no matter how tempting this may be! Some pond experts go so far as to recommend only one-half inch of fish per 10 gallons of water as a maximum stocking density.
On occasion, you may encounter ponds crowded with 2 or even 3 inches of fish per 10 gallons of water and the fish seem to be fine. However, the density and ecological strain of this loading turn these ponds into fragile systems. The pH tends to sag, the fish tend to grow more slowly, and disease can become a common occurrence.
It's very difficult to salvage sick fish in a pond that's overcrowded. Most likely, Mother Nature will eliminate some of your customer's fish to achieve the ideal stocking density based on the system the fish are in, and then the remainder may recover. So advise your customer to reduce the number of fish if their pond is overstocked.