Avoid stocking too many fish or allowing the fish population to become overabundant through excessive feeding and no harvest; especially having too many fish present during winter. Nitrogenous wastes/ammonia is processed slower during cold water conditions, thus it can be a greater problem during cold water conditions.
Despite what is often preached by aeration sales people that ammonia can be dissipated, degassed or stripped by aeration and bubbling, this is NOT true. Ammonia will continue to increase at normal pH's despite lots of oxygenation of the water. Ammonia is basically processed or reduced by direct plant uptake and ammonia is broken down or reduced by nitrifying bacteria.
