Abstract: A system is disclosed for drawing water from the top and bottom of an aquarium simultaneously for delivery to a filter. This system includes at least one subsurface tube connected to the lower portion of the back wall of the aquarium and brought to an external tank mounted to the back of the aquarium proximate to the surface water line. A horizontal rectangular opening at the surface water line of the aquarium allows the surface water from the aquarium to flow directly into the external tank. At least one drain tube leads from the external tank to an external algal or bacterial filtration system or simply to an overflow reservoir. Adjusting the height of the distal end of the subsurface tube within the external tank increases or decreases the hydraulic pressure in the subsurface tube, thus changing the proportional amount of water in the external tank being drawn from the bottom of the aquarium relative to that being drawn from the surface. Free of moving parts, the system will not harm tiny specimens.

Abstract: An apparatus for creating surges in an aquarium uses a pump to move water from the aquarium into an external tank. A siphon tube periodically creates surges by draining water from the tank back into the aquarium. The siphon tube has an inlet at a predetermined elevation within the tank, an outlet for discharging water from the tank into a smaller secondary basin, and an intermediate high point at an elevation above the inlet. The secondary basin has a series of water dispersion outlets that allow the surge to discharge into the aquarium. The siphon tube allows water to surge from the tank into the secondary basin and thence back into the aquarium when the water level in the tank rises above the high point of the siphon. The surge continues until the water level falls below the inlet to the siphon. The pump continues to pump water from the aquarium into the tank at a relatively constant rate throughout this entire process, but at a lower flow rate than can be drained by the siphon tube.

Abstract: An algal filter that purifies and oxygenates aquarium water comprises an elongated box with an inlet and an outlet at opposing ends with supports along the interior of the bottom wall. Trays having a lattice construction rest on the supports. Algae grow on the trays when the trays are contacted by water. A flow of water along the box is induced by a pump. Baffles are situated above the trays in alternation with the supports to alternately direct the water upward and downward through the trays along the length of the filter to produce a turbulent flow of water that potentiates the growth and metabolic exchange capabilities of the algae. Slots in the baffles induce a side to side flow that further enhances turbulence. In addition, the lattice construction of the trays results in quiet areas among the turbulence which may be used as refugiums by plankton and other small organisms.