How to Add an Overflow to a Tank

An overflow in an aquarium tank allows the aquarist to incorporate a sump into the system. Sumps are reservoirs or containers that are positioned behind or below a tank and are connected to it with pipes and tubes. Aside from increasing the overall volume of water in the system, sumps allow the aquarist to hide unsightly pieces of equipment. Aquarium pumps and various types of filter material and heaters can be placed in the sump. A correctly designed and constructed tank overflow channels the aquarium water via pipes to the sump from where it is returned to the tank through a pump.

Things You'll Need

  • Aquarium, 36 inches long by 12 inches wide by 12 inches high, with base pane pre-drilled with one 0.72-inch diameter hole, in the back left-hand corner
  • 30-gallon sump
  • 0.72-inch diameter bulkhead
  • One washer, 0.72-inch diameter
  • 10-inch PVC pipe, 0.72-inch diameter
  • Tube of non-toxic, 100-percent silicone sealer
  • Two pieces of glass, 10 inches long by 3.5 inches wide by 0.31 inches thick
  • 140 gallon-per-hour submersible pump
  • 5-feet flexible plastic pipe, 0.2-inch diameter
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Instructions

    • 1

      Position the 30-gallon sump directly under the pre-drilled hole in the aquarium's base pane.

    • 2

      Place a tablespoon of non-toxic silicone sealer around the 0.72-inch diameter hole in the base of the aquarium.

    • 3

      Push the washer over the threaded end of the 0.72-inch diameter bulkhead and place this threaded end through the pre-drilled hole in the base pane of the aquarium. Push the washer into the silicone and spread the sealer around the washer to create a water-tight seal.

    • 4

      Place the nut onto the bottom of the thread and tighten. Allow the silicone 24 hours to cure.

    • 5

      Push the 10-inch long PVC pipe over the thread of the bulkhead from underneath the aquarium. Place a tablespoon of non-toxic silicone sealer around where the surfaces join and spread the sealer over the join to create a water-tight seal.

    • 6

      Run a continuous bead of silicone sealer along the side edge of one of the 10-inch long sides of the first piece of glass. Place this piece, silicone side down, onto one length side of the second 10-inch long piece of glass to form the shape of a right angle.

    • 7

      Hold the pieces together for a few minutes and then stand them in a vertical position to cure for 24 hours.

    • 8

      Run a continuous bead of silicone sealer along the side edges of the bottom of the shape and along the side edges of both sides of the shape.

    • 9

      Place the structure into the left-hand corner of the aquarium. The pre-drilled hole must be inside this structure. Allow 24 hours for the silicone to cure.

    • 10

      Attach the 5-foot plastic tubing onto the exhaust nozzle of the submersible pump and place the pump into the sump. Hang the opposite end of the pipe over the aquarium rim at the opposite end to the pre-drilled hole.

    • 11

      Secure this end to the aquarium rim with a plastic clamp.

    • 12

      Fill the aquarium until water begins to flow over the vertical 10-inch high glass structure. The water will fall to the floor inside the cubicle created by the structure and flow through the pre-drilled hole and pipe into the sump.

    • 13

      Allow the sump to fill to the half-way mark with water.

    • 14

      Plug the submersible sump pump into a power source and turn it on.