How to Make Plexi-Glass Fish Tanks

Written by kasandra rose
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How to Make Plexi-Glass Fish Tanks
Acrlyic aquariums transmit more light than glass aquariums. (aquarium image by Henryk Olszewski from

Plexiglass, or acrylic, can be crafted into showcase aquariums and allows you the flexibility to make an aquarium to fit a particular space. These directions are for a fish tank 6 feet long, 2 feet deep and 2 feet high. Check the references to learn how to adjust the measurements to make other sizes --- especially the thickness, since the plexiglass thickness needed varies with tank height. Building an acrylic aquarium is a two-person job.

Skill level:

Things you need

  • 4 1/2-inch-thick "Cell-Cast" acrylic sheets, cut by the supplier to 6 feet by 2 feet
  • 2 1/2-inch-thick "Cell-Cast" acrylic sheets, 24 inches by 23 inches
  • Acrylic scrap pieces
  • Measuring tape
  • Weld-on #4 solvent cement
  • Aquarium-safe silicone
  • Solvent bottle
  • 2 to 3 rolls of electrical tape
  • 2 sawhorses
  • 1 drop light
  • Jigsaw or sabre saw with a plastic blade
  • Spray bottle with water
  • Drill
  • Scissors
  • Felt marker
  • 2-flute square-cut router bit

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  1. 1

    Call various suppliers to determine the most reliable plexiglass for the best price and have pieces cut. All cuts must be exact to within 1/16th of an inch. Have the edges routered for a clean, finished appearance. Take your measuring tape with you when you pick up the pieces and measure each piece before accepting the work. Also pick up some scrap pieces of acrylic.

  2. 2

    Draw 2 openings, 28 inches long and 15 inches wide, in the top piece of acrylic using a straight edge and a felt marker. The openings should be centred on each half of the tank and four inches from any side with an 8-inch support space left in between the two openings.

  3. 3

    Put wood supports beneath the plexiglass to keep it from bending or cracking while you cut and drill. Drill some holes along the cut line with the drill. Don't centre the drill on the cut line --- this will make your cut too wide. Drill enough holes to allow your sabre saw to fit into the hole, then cut to one corner, remove the saw and cut to the other corner. Spray water on the area as you work to keep the blade from melting the plastic. Drill these pilot holes on all four sides and cut cleanly to the corner. You may need to clean up the edge a bit with the saw where the original holes were drilled.

  4. 4

    Remove 1 inch of paper from all edges of the acrylic by peeling carefully and cutting away the paper with scissors.

  5. 5

    Run the 2-flute straight-cut router bit lightly down each edge of the scrap plexiglass for practice. Do this by hand to remove the rough spots made by the saw. Keep the edge of the bit flat against the acrylic edge. After you are confident in your scraping technique, do the same thing on each acrylic piece to be used for your tank.

  6. 6

    Practice your joining technique using the scrap pieces and applying the Weld-on #4 solvent cement using the plastic bottle. Run the solvent slowly along a joint between two pieces of scrap, leaving no holes. The solvent should seep completely into the space between the plexiglass pieces and dissolve the acrylic, melting it together. You want no holes and can only reapply the solvent within a few seconds or you will weaken the joint.

  7. 7

    Lay 2-by-4s flat on the ground and lay the piece of acrylic that will become the bottom of your aquarium on top of them, bottom side down.

  8. 8

    Cut 6-inch pieces of electrical tape and secure them beneath the acrylic aquarium bottom with half of the tape extending out to the sides every 4 inches on all four edges of the bottom.

  9. 9

    Place the piece of plexiglass that will be the back on the bottom acrylic piece, carefully matching the outside edges, and secure it with the electrical tape attached to the bottom. Do not pull the tape tightly. Do this for all four sides.

  10. 10

    Tape the side corners together with the electrical tape every 4 inches.

  11. 11

    Shine the light inside the tank and slowly apply the Weld-on #4 solvent cement generously around the interior joints of the bottom only, not the vertical joints of the sides. Check for gaps and bubbles constantly, adding more solvent within a few seconds. If the solvent doesn't penetrate across the whole joint, immediately add more from the outside as well.

  12. 12

    Let the tank dry for a minimum of 4 hours.

  13. 13

    Place the tank on its back and weld the two back edges that are now horizontal. Wait 4 hours before moving the tank.

  14. 14

    Put the tank on its front and weld the two front edges. Do not disturb the tank for 4 more hours.

  15. 15

    Put the top on the tank, lining up the edges, and secure it with electrical tape. Place the sawhorses next to the tank; lift the tank and flip it over onto the sawhorses. The top of the tank should now be on the bottom and you should be able to get inside the holes to seal the joints with Weld-on #4 solvent cement. Check that the tank top has not shifted while flipping it before welding with the solvent. Do not move the tank for 4 hours.

  16. 16

    Flip the aquarium right side up and check for bubbles and gaps. Fill gaps with aquarium-safe silicone sealant. Wait 72 hours before filling the tank if you used no silicone sealant and 120 hours before filling the tank if you used silicone sealant.

  17. 17

    Move the aquarium to its permanent location; remove the plastic protective coating and all the tape. Fill slowly, watching for any leaks. If leaks are found, drain the tank completely, dry the inside and apply silicone sealant to the leaking areas.

Tips and warnings

  • Check at the plastic supplier for solvents, solvent bottles and silicone.
  • If you intend to put in any acrylic structures such as overflows into the tank, assemble them when you're sealing the bottom and then weld them to the back while the tank is on its back.
  • You can add structural strength to the bottom corners by cutting a triangle of acrylic and welding it to each corner.
  • Do not remove the plastic covering on the plexiglass sheet until instructed to do so; it protects the acrylic from scratches.
  • Plan on making only straight cuts with the sabre saw.
  • When welding the acrylic joints together, you want no holes and can only reapply the solvent within a few seconds or you will weaken the joint.
  • Keep someone nearby for safety while you are under the tank.
  • Anything that touches the acrylic and solvent will be permanently stuck to the tank. Make sure that nothing comes in contact with the weld solvent.
  • Spills across the face of the acrylic will mar it permanently. Special care is needed when welding the front panel and the top piece.

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