Powerheads are available in a range of sizes to suit different size aquariums and accessories. Some are equipped with a venturi device, which adds a stream of air bubbles to the outgoing flow (but reduces the overall turnover rate). Most have an adjustable output direction, and some have a flow speed control. Charterhouse Aquatics stock a huge range of powerheads available from all the biggest brands including EcoTech Marine, Maxspect, TMC, Jecod, Aqua Medic plus loads loads more