How to Build a 3D Aquarium Background


Custom aquarium backgrounds add huge appeal to your tank, contributing naturalistic depth and elegance to otherwise plain glass. Additionally, homemade aquarium backdrops can make fish feel more secure, and provide colonization sites for groups of beneficial bacteria. While these backdrops can be ordered from a number of retailers, customization is limited and prices are often outlandish, sometimes in the hundreds of dollars for even a 10-gallon-size background. With a little DIY creativity, you can easily make your own custom 3-D aquarium background.

Things You'll Need

  • 1/2 inch Styrofoam sheeting
  • Serrated knife
  • Aquarium silicone
  • Craft knife
  • Sandpaper
  • Heavy plastic (or other work surface)
  • Water-safe concrete mix
  • Concrete dye
  • Sifter or piece of mesh
  • Paintbrush
  • Mixing bowls

Measure and cut a rectangle out of the Styrofoam to fit the back of your aquarium, minus 1/4 inch on each side (to allow room for the layer of concrete). For tanks larger than 30 gallons, you may want to create the background in two or three pieces for easier installation. Make the breaks between segments somewhat irregular for a more natural look, rather than straight lines.

Cut the openings for your filter housing and heaters in the Styrofoam.

Glue additional pieces of Styrofoam to the front of the first sheet to create depth. Coat the back of the pieces in a thin layer of aquarium silicone, and press firmly onto the larger sheet.

Carve into the Styrofoam, creating crevasses and detail using a craft knife and sandpaper. Use images you like to get a basic idea. You can model your background after slate slabs, stacked river rock, driftwood, etc. Exaggerate the detail, since a layer of concrete will be covering the finished product. Continue carving and gluing until you have a look you like. This is the time for true customization.

Lay the Styrofoam out on top of the heavy plastic.

Sift your concrete in batches through the sifter or mesh to remove any large particles and stones.

Mix the sifted concrete according to the package directions, adding a little extra water. The mix should be somewhat soupy so that it can be applied with a brush.

Apply the concrete to the surface of the foam, working quickly. Coat the entire surface evenly in one layer, and immediately add the second layer before the concrete has a chance to dry. Mist with the spray bottle often as you go. Continue adding concrete to build up the 3-D background, and use the brush to add texture while the mix is wet. Add concrete dye to a smaller batch of concrete, and use to create shadows and drips.

Allow the background to cure slowly according to the product directions. Most concretes will cure harder if they are kept moist for the first 24 hours, so frequent misting can help.

Install in the tank by coating the back of the Styrofoam with a layer of aquarium silicone. Press firmly onto the glass. Let the silicone dry for 24 to 48 hours.

Fill the tank with water only once the concrete and silicone are completely cured. The concrete will continue to leech chemicals into the water for up to a month, depending on brand and composition, so plan on changing the water at least every three days for at least two weeks. Check your pH, chloramines, and hardness often; once they level out, you are ready to add fish.

Tips & Warnings

  • For the first six months or so with your custom 3D aquarium background up and running, you may have trouble getting the hardness down in your water. Live plants, RO water, and peat moss in the filter can all help correct this.
  • Do not get hasty or lazy on Step 11. You can kill off all of your fish if you try to add them into the tank as soon as the concrete has cured. Check your water parameters, and check them often.

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