These variable flow pumps are dedicated to the traditional ornamental pond owner.variflow pumps are growing in popularity with many first adopters running them ‘dry’ for use with koi ponds.these new strainer models offer all the benefits of the original variflow but come complete with a strainer cage for submersible use. They can be still run dry if required.variable flow pumpsthe most sophisticated variable flow pumps can have their power turned up or down as required. This provides a number of benefits. For instance a waterfall could be increased in force during summer months or to impress visitors whilst the same waterfall could be reduced to a trickle at night time to reduce noise levels. Similarly a pump could be turned high in the summer water oxygen levels low and low in the winter turning the power down saves on energy considerably.