DIY: Fiberglass Tank

Though potentially challenging to build, a fiberglass aquarium combines strength and durability in a lightweight tank. Fiberglass designs work best for tanks bigger than 100 gallons, as the cost of building the tank begins to compete with the price of a large pre-made glass or acrylic aquarium. You must take care and seal all parts of the aquarium from water, as even a little water leaking from the tank will ruin the wood and fiberglass structure. By itself, wood is susceptible to dents and scratches that render the tank useless. Adding fiberglass sheets helps give the wood more durability.

Things You'll Need

  • Plywood
  • 2-by-4-inch boards
  • Galvanized screws
  • Galvanized bolts
  • Wood filler
  • Sandpaper
  • Marine epoxy resin
  • Fiberglass cloth
  • Scissors
  • Aquarium-safe silicone
  • Glass sheet
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Instructions

    • 1

      Draw a scale model of the aquarium. All sides but the front will incorporate plywood and 2-by-4-inch boards held together with galvanized screws and bolts. You must form a skeleton of the aquarium with the 2-by-4 boards and then form the tank part on the inside with the plywood. The fiberglass will go over the plywood on the inside of the aquarium.

    • 2

      Build the skeleton of the aquarium using the 2-by-4 boards. For larger aquariums, space out the wood every foot so it forms a structure that can withstand the force of the water when the tank is full. Secure the wood using galvanized screws and bolts.

    • 3

      Cut and place the sheets of plywood on the inside of the aquarium. Countersink the screws used to attach the plywood to the skeleton. The plywood sections should not have large gaps between the boards.

    • 4

      Fill the screw holes with wood filler, and sand the entire structure smooth with sandpaper, paying careful attention to the inside of the aquarium.

    • 5

      Apply a coat of marine epoxy resin on the inside and outside of the aquarium; do not miss any spots. The sealant on the outside will prevent the wood from rotting due to the humidity created by the large volume of water in the aquarium. Use three coats on both sides.

    • 6

      Cut fiberglass cloth with scissors to fit, and lay it on the plywood on the inside of the tank. Check to ensure it fits properly, then coat it with the marine epoxy resin. The fiberglass cloth will turn nearly transparent when saturated; if you see any bubbles, wet them and smooth out the fiberglass immediately. Apply three to five coats of resin. Let the resin dry and cure before proceeding.

    • 7

      Seal the seams on the inside of the aquarium with aquarium-safe silicone. The epoxy should have sealed the edges, but a layer of silicone will fill any small holes that remain. Let the silicone cure.

    • 8

      Fit a glass sheet to the front of the aquarium, sealing the edges with silicone. The water pressure will hold the glass up, but you can add small supports so it doesn't fall out when you are transporting the aquarium.

    • 9

      Fill the aquarium with water, then check for and mark any leaks --- including damp spots. Drain the tank, then coat leaky spots with extra epoxy and silicone. Let the epoxy and silicone cure.