DIY Sump for Freshwater Aquariums

Written by robert boumis
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DIY Sump for Freshwater Aquariums
Though popular with saltwater tanks for years, sump filters have only recently become used for freshwater setups. (Jupiterimages/ Images)

Sump filters, also known as wet-dry, trickle or overflow filters, are renown for their biological filtration. They require surprisingly little maintenance, but are more challenging to assemble than most other types of aquarium filters. While the task of assembling them may appear daunting at first, the logic of their design becomes apparent as they are assembled. Still, there are many steps where things can go wrong, including floods and burnt-out pumps. With care, you can assemble your own sump tank.

Skill level:
Moderately Challenging

Things you need

  • Smaller aquarium, or suitable-size glass or acrylic box
  • Dry-erase marker
  • Cling film
  • Acrylic overflow box
  • Plastic return spigot
  • Aquarium pump
  • Baffles
  • Filter media
  • Heaters, skimmers, and secondary filters
  • Vinyl tubing (length and diameter will vary with your design)
  • Dechlorinated water
  • Permanent marker

Show MoreHide


  1. 1

    Leak-test your sump, either in a smaller aquarium or a suitably sized acrylic or glass box. The best way to leak-test is to fill the sump, mark the level with a dry-erase marker, then cover the sump tightly with cling film. If the water level remains unchanged after 24-48 hours, the sump is watertight.

  2. 2

    Attach the overflow box and the return spigot to the main aquarium. This will vary slightly depending on the brand or design of your overflow box. Some just hang on the tank, while others require drilling the glass itself.

  3. 3

    Install baffles in the sump and overflow box. Again, this will vary considerably depending on the brand or design of your filter.

  4. 4

    Place filter media, aquarium heaters, skimmers, secondary filters and the return pump into your sump. One of the perks of a sump filter is that you can hide all of this unsightly equipment in the sump.

  5. 5

    Run the vinyl tubing from the overflow box to the sump, and from the return pump to the return spigot.

  6. 6

    Fill the tank (if you have not done so already) and the sump with dechlorinated water. Mark the water level in the sump with a permanent marker and label this line "max fill, pump off." Whenever you add water to the sump (with the return pump off), do not fill it past this line.

  7. 7

    Prime all secondary filters and pumps. Almost all aquarium pumps and filters need to be filled with water before you can turn them on.

  8. 8

    Turn on the aquarium. Once water begins to come out of the return spigot, mark the new water level in the sump and label it "max fill, pump off." Whenever you add water to the sump (with the return pump on), do not fill it past this line.

Tips and warnings

  • Consider adding check-valves to the return line.
  • DIY sump filters can vary considerably depending on your design. Be prepared to improvise.
  • Do not activate any aquarium equipment dry. This will burn out pumps, crack heaters and generally ruin your day.
  • Do not submerge any filter not designed to be submerged. This can cause shock hazards and will ruin your pump.

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