How to Build a Stream in a 40 Gallon Aquarium

Written by amy reynolds
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How to Build a Stream in a 40 Gallon Aquarium
Recreate a natural stream in your aquarium (Stream image by Dave Johnson from

A miniature stream capable of mimicking nature on a small scale is possible in a 40 gallon aquarium with minimal maintenance. Choose the aquarium design most appropriate for your needs. The 40 gallon aquariums come in two different dimensions, breeder 36 by 18 by 16 inches or long 48 by 12 by 16 inches. For a more winding path of the stream, choose the shorter and deeper breeder aquarium. The 40 gallon long aquarium will more readily fit a longer, straighter stream path but require more height adjustments. Use creativity to get the desired result for appearance of a moderately difficult project.

Skill level:

Things you need

  • 4 to 6 large tubes of clear silicone aquarium sealant (caulking gun size)
  • Caulking gun
  • Plexiglas, 6 inches high, and 1 inch longer than aquarium length
  • Rocks and gravel
  • Aquarium filter, hang on back type
  • Tubing for pond or aquarium use, diameter to match filter intake tube
  • 13.6 to 18.1kg. potting soil
  • Various pieces of 4- or 6-inch PVC pipe
  • Ground fault interrupter

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  1. 1

    Set the aquarium on a sturdy stand. Make sure the stand supports the entire base of the aquarium. The weight can easily reach 181kg. Check you have an accessible socket.

    How to Build a Stream in a 40 Gallon Aquarium
    Use an aquarium stand to hold the weight of the tank. (Aquarium image by crossgolfing from
  2. 2

    Use silicone aquarium sealant to caulk the Plexiglas piece into place, on its side, approximately 5 inches from the front of the aquarium, against the bottom, to build a water-holding area. A slight bow from the extra inch of length will make it easier to hold in place and add visually to your design. Caulk both ends and bottom, on both sides to seal all edges to the glass. Allow the silicone to cure according to manufacturer's directions.

    How to Build a Stream in a 40 Gallon Aquarium
    Use the same method to caulk as you would with tile. (glazier image by Greg Pickens from
  3. 3

    Apply a layer of silicone sealant over the entire face of the Plexiglas, then place gravel and rocks on it. This should cover the Plexiglas and give it a natural appearance. Stones and gravel that fall to the bottom of the tank will form the bed of the stream in that area. Take your time with this to get the look you want. Allow the silicone to fully cure.

    How to Build a Stream in a 40 Gallon Aquarium
    Attach rock for visual interest. (gravel image by Alison Bowden from
  4. 4

    Attach a long piece of tubing to the intake tube of the hang on back filter you've chosen, using silicone sealant. Allow the silicone to cure. Place the water intake tube across the land (back) area and down into the water area at the front of the aquarium. Trim the water intake tube close to the bottom of the aquarium. Secure the tube in place with silicone sealant and rock. Allow to dry.

  5. 5

    Fill the back section of the aquarium--behind the Plexiglass barrier--with potting soil almost to the top of the divider. Add water almost to the top of the divider in the front section. Add soil and water a little at a time, alternating between the two to keep pressure from breaking the silicone seal. The stream will run from the filter, down your designed PVC-tube path, across the front of the water section and back up through the intake tube and keep recirculating.

    How to Build a Stream in a 40 Gallon Aquarium
    Use potting soil or other quality soil. (preparing soil for garden image by Cherry-Merry from
  6. 6

    Lay whole pieces of PVC to decide where your stream should flow, meandering toward the opposite end, into the water/filter area. Cut pieces of PVC in half, lengthwise, after deciding the layout of your stream. Attach a halved elbow or short, straight piece of PVC pipe, cut side up, to divert water to the overflow of the filter. Seal all openings between the back of the overflow and the edge of the PVC pipe and place the filter on one end of the aquarium. Add rockwork using the same method you used for the dividing wall to camouflage the silicone and PVC.

    How to Build a Stream in a 40 Gallon Aquarium
    Use PVC pipe to form your stream. (coude en pvc de 45° image by Marie-Thérèse GUIHAL from
  7. 7

    Continue adding straight and curved pieces of PVC cut in half, cut-side up, until you reach the other end of the aquarium. End with a small overlap to edge of the water. Use sealant to secure the pieces of PVC together in place to form the stream path.

  1. 1

    Fill the filter with water and have more ready to add, as needed, to keep the stream and front water area full. Add water in the front area and stream, as necessary. Plug in the ground fault interrupter and filter, and adjust the water flow. Turn off the water flow if you have any leaks or runoff. If you have leaks, dry with paper towels or cloth and add silicone sealant where needed.

  2. 2

    Turn off the water flow and dry the area once the stream is flowing correctly and you have no leaks. Use silicone caulk to attach rocks and gravel, covering all exposed piping and tubing. Allow the silicone to dry, according to the manufacturer's directions.

  3. 3

    Add water, plants, fish and any other decor to finish your stream in a 40 gallon aquarium. Add water, as needed, to replace evaporation.

Tips and warnings

  • Use different rock types in different areas.
  • Look at pictures of streams for more ideas.
  • Add terrarium plants, small fish and amphibians.
  • Use full-spectrum lighting on a timer.
  • Always use a GFCI, ground fault circuit interrupter, device or outlet when using electricity and water

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