Air pump (aerator)
Device that injects air into the water via an air stone. Increases oxygenation and circulation, useful in emergencies and in ponds.
Detailed explanation
The air pump produces a flow of air which, injected into the water via a porous stone, creates bubbles that agitate the surface, increasing gas exchange.
Situations in which it is essential: quarantine aquariums, emergencies (electrical blackout), ponds in summer, aquariums without filters.
In planted freshwater aquariums the air pump must be turned off during the photoperiod because it disperses the injected CO2.
The quietest brands are Eheim Air, Tetra APS, JBL ProSilent. A non-return valve between the pump and the aquarium prevents the water from siphoning.
In the pond, air pumps are essential in the summer for oxygenation and in the winter to maintain a hole in the ice.