Why Is My Fish Digging? Gravel Moving Explained

You go to bed with a neat aquarium and wake up to a crater in the gravel, a plant floating at the top and a pile of pebbles against the glass. Somebody's been digging. Most of the time it's normal fish behavior, but it's worth knowing why.

Reason 1: They're looking for food

Lots of fish sift the bottom for food:

• Corydoras push their snouts into the sand.
• Loaches burrow and dig all day.
• Goldfish suck up gravel and spit it out.
• Eartheater cichlids take mouthfuls of sand and sift it through their gills.

This is healthy. If they're doing it constantly, it may mean they're hungry, or food is getting lost in the gravel. Use sinking food and see whether they settle down.

Reason 2: They're building a nest

Many cichlids dig pits to spawn in. Convict cichlids, kribensis, firemouths and many others move a surprising amount of gravel before laying eggs. Signs it's a nest:

• Two fish working together on one spot.
• Brighter colors.
• One or both fish chasing others away from it.

If you see eggs, the other fish in the tank may get chased hard. Have a plan for separating them.

Reason 3: They're claiming territory

Some fish dig to rearrange their space or mark out an area, especially cichlids. Breaking up the sight lines with rocks and plants can calm it down.

Reason 4: Crayfish and crabs

If you keep a crayfish, it's almost always the culprit. They dig burrows, move rocks and uproot plants. See can crayfish live with fish.

When digging is a warning sign

• Rubbing or "flashing" against the bottom. This is different from digging. Fish that scrape themselves on gravel may have parasites or irritated gills. Test the water.
• Gasping at the surface along with digging. Check ammonia and oxygen.
• Torn fins or hiding fish in a tank with a new digger. Someone's guarding a nest.

Keeping your plants planted

• Choose a substrate that matches the fish. Diggers like sand; see the best substrate for a river tank.
• Put big stones around plant bases.
• Use plants that grow on wood or rock, like Java fern and anubias, which diggers can't uproot.
• Glue rocks in place if a fish keeps knocking over a stack. Rockwork that falls can crack the glass.

Most digging is a sign of a healthy, busy fish. Give it a place to do it.

Sources (2)

Smart Aquarium Guide: Why Do Corydoras Keep Digging? · Go Fish Aquariums: Cichlid Digging Behaviour

Photo by zoosnow on Pixabay.

Related: Ten Fish That Thrive Best In A River Tank Style Aquarium (Riparium) · Are Fish Omnivores?