For aquaria different kinds of pumps are used: from simple air lifts to high-efficient industrial pumps a large field of applications are possible.
For water feed from filter sump back to the aquarium (overflow system) it is important that the pump has not only a high flow (l/h) but enough pressure (m), too. The effective flow is shown in a pump diagramm: if you know the head (A) go from it horizontal to the graph. At this point you go downwards to the X-axis. This point is the effective flow of the pump under this conditions.
For producing currents inside of the aquarium you need pumps with very low pressure but with very high flows. As standard you should choose 5 times the aquarium volume per hour for feed pumps from filter sump to aquarium. For currents take 10 times the aquarium volume per hour.
Universal pumps are suitable for creating curents, for filters and for supplying water to filter systems.
Energy Saving pumps are best for applications, that runs all the time, like supply pumps and current pumps.
Robust magnetic coupled industrial pumps for seawater applications. Ideal for AquaCare large skimmers.
Dosing pumps are used if small water flows with high precision are required, e.g. lime reactor, lime water reactor, additives.
Air pumps are used for aerating (e.g. neutralization stage of Turbo Chalk Reactors), for air lifts and for skimmers with wooden air stones.
Typical applications for pressure pumps: reverse osmosis unit, micro filtration units, heights with more than 10 metres.