How to Make a Tunnel in an Aquarium

Many fish spawn in caves.
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Some aquarium decorations go beyond aesthetic appeal. Many species of fish, including various plecos and cichlids, need tunnels or caves to feel safe and spawn. A customized tunnel of your own design can add a focal point to your tank and encourage more natural behavior in your fish.


This project requires a few common materials and simple tools. Start with a length of plastic pipe, such as PVC or ABS pipe, as long as they are rated as "food safe." Pick the diameter of the pipe based on the size of your tank and the size of your fish. You also will need a cutting tool. A hacksaw works fine, though a rotary tool or Dremel will make the job go quicker. This project also will require aquarium glue and aquarium gravel or aquarium rocks, which you can pick up at most pet shops. Also, be sure you have safety goggles.


For the first step, cut your pipe to the desired length, based on your specific species of fish and the size of your tank. Once it's the right length, cut it horizontally, creating two half-pipes. If you did this correctly, the pipe will form a sideways "C" shape. Then, cut the front and back of the pipe inward to give it a less artificial shape.


Glue rocks or gravel to the outside of the PVC pipe using aquarium blue. Use only rocks and gravel from pet shops, as other rocks may dissolve and damage water chemistry, or have dangerous chemicals on their surface. Cover the outside of the pipe with your rocks or gravel. You also can cover the inside if you like. The entire step of gluing rocks to the outside of the tunnel is optional if the tunnel is not intended for a display aquarium. In a breeding tank or quarantine aquarium, you can skip this step.


Follow the instructions on the aquarium glue for curing. Most brands take 24 to 48 hours to cure completely. Once enough time has passed, soak the tunnel briefly in water and rinse it. This removes dust from the rocks, and any chemicals the glue released during curing. Do not do this in the aquarium itself.

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