Structure provides hiding places for small fish, which concentrates bigger fish making fishing for them easier.
Large fish without structure will swim constantly looking for food causing them to spend more energy finding food that they gain from eating it.
Ponds with structure produce more forage fish per acre resulting in larger and healthier fish.
Ponds with low alkalinity do not produce natural foods required to support forage fish to feed big fish. Adding lime to a pond improves the availability of required nutrients.
Planktonic algae form the base of the food chain in a pond and shade out nuisance vegetation. Fertilizer increases algae growth just like garden fertilizer stimulates plant growth.
Do you have old pond syndrome? As ponds age the muck on the bottom of the pond releases hydrogen sulfide and phosphorous. Hydrogen sulfide and can result in poor reproduction of forage fish such as bluegill. Phosphorous causes excessive algae blooms which can cause low oxygen. Bacterial pond treatments consume excess nutrients and sludge improving water quality and fish production.
Even balanced populations in sustainable ecosystems can be improved upon.