Abstract: An electrical heater is combined with a thermostat in a sealed enclosure itself sealed in a glass tube, the enclosure comprising two tubes telescoped together, one being translucent and containing the thermostat and the other being of electrically insulating material, e.g. ceramic.

Abstract: Aquarium filtration equipment in the form of an under gravel or sub-gravel filter, the equipment comprising a synthetic plastics plate from the general plane of which a plurality of substantially regularly spaced columns project downwardly, their lower ends being contained in a common plane which is inclined to the general plane of the plate, said plate also comprising means for connecting an airlift or other water circulating means thereto at a location on said plate where the spacing between the inclined general plane of the plate and the common plane containing the lower ends of the columns is at substantially its maximum.

Abstract: An electrical heater comprises a sealed glass tube containing a sealed tubular structure formed by, (a) a metal tube containing an electrical heating element insulated from the metal tube, and (b) a plastics tube sealed to one end of the metal tube and containing a thermostat for the heating element.