Why do Corydoras Keep Digging in Sand?

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If you’ve never had a catfish before, your Corydoras’ behavior may catch you off guard.

After all, you’re not used to seeing fish digging and burying themselves in the substrate too often. Fortunately, there’s nothing concerning about the behavior.

Corydoras dig into the sand for eating purposes. They perform what’s known as sand sifting, which is the fish taking in mouthfuls of sand and eliminating it via the gills.

What’s left in the fish’s mouth is often food like insect larvae, microcrustaceans, and other types of organic matter with nutritional properties.

Corydoras also use sand as a hiding spot when housed with more aggressive or invasive fish species that don’t care about your catfish’s boundaries and personal space.

In other words, Corydoras require sand.

How Deep Do Corydoras Dig?

Corydoras won’t dig too deep into the substrate. Their goal is to sift the sand for food which is typically located on the surface.

So, you only require up to 2 inches of sand to accommodate even the larger species of Corydoras.

Do Corydoras Dig Up Plants?

Not intentionally, no. That being said, it can happen for a more energetic Corydoras to unearth more sensitive plant species with softer and shorter roots.

To prevent such a scenario:

  • Introduce plants first – You should always plant your plants first and only add the fish several weeks later. This allows the plants to grow and anchor themselves properly in the substrate to withstand Corydoras’ activity.
  • Choose your plants carefully – If you want resilient and strong plants, go for species like cryptocoryne, amazon sword, Vallisneria, or dwarf hairgrass, among others. Be careful not to cover the entire substrate. Otherwise, your catfish won’t have sufficient sandy areas to search for food. If you have a smaller tank, you would be better off with floating plants instead.
  • Secure the plants – If your Corydoras keep bothering the plants, surround the plant’s stem with some harmless aquatic decorations. These will discourage the catfish from digging in that area. Just make sure you avoid rugged or dangerous materials or sharp rocks that could hurt your catfish.

Also, it’s not uncommon for underfed Corydoras to dig up plants specifically to eat them.

You can circumvent this problem by feeding your catfish properly, both in terms of nutrients and feeding frequency.

How to Stop Corydoras from Digging?

This is a sensitive topic, given that Corydoras are natural sand diggers. So, you can’t really stop them from digging into the substrate.

If there’s sand, your cory catfish will stir it up frequently. This being said, you can discourage your Corydoras from digging in specific areas.

Consider the following:

  • Proper feeding – I’ve already mentioned this point. Corydoras are more likely to dig up rooted plants if they’re starving. These fish have omnivorous diets, so they consume both animal protein and plant matter. If your Corydoras seem to have developed a preference for live plants, supplement their diet with more algae tabs and veggies. They will lose interest in your live plants shortly.
  • Bury treats – Your plants will, ideally, only occupy specific areas in the tank, preferably near the tank’s walls. The middle area should consist of open space for the catfish to dig around the sand as it sees fit. You can bury algae tabs or even shrimp pellets into the sand (keep it shallow) to incentivize the catfish to dig them up. Corydoras are smart fish, so they will soon learn where the food is and will prioritize those areas when looking for their regular meals. Soon, they will lose interest in digging other portions of the tank.
  • Secure the plants better – Mix some gravel in the sand surrounding the plants or use rocks to create a barrier near the plants’ stems. These will often discourage corys from digging the area since it’s too much trouble.

It’s important to note that you can actually train your Corydoras to only dig in specific areas in the tank.

You only need patience and some ingenious diversions to keep the cory’s attention where you need it to be.

Do Corydoras Burrow Themselves in Sand?

Yes, Corydoras do bury themselves in the sand occasionally, but this isn’t frequent behavior.

They only bury themselves when stressed, to hide from more aggressive tankmates, or when playing or resting.

They can sometimes go off the radar completely by burying themselves head-to-tail.

Will Corydoras Dig in Gravel?

Yes, Corydoras also dig in gravel because they can’t distinguish between good and bad substrates.

This is where you need to grow into a better man/woman and decide for them. Gravel might be nice, but it isn’t suitable for Corydoras due to their feeding tendencies.

Corydoras that attempt to sift gravel end up bruising themselves or even experiencing more severe traumas around the mouth and gills.

These are sensitive areas in Corydoras, causing the catfish to prefer sand over anything else. You can mix in some gravel occasionally, as I’ve mentioned before, to protect plants, for instance.

Corydoras will learn to avoid those areas and stick to sand-rich zones instead.

But you shouldn’t use gravel alone in your Corydoras tank, as this isn’t optimal for them.

Conclusion

Corydoras are born diggers and substrate dwellers, so you can’t change their behavior.

However, you can discourage them from avoiding unearthing plants or stirring up the substrate too often.

Test things out, see what your cory likes and dislikes, and come back with some feedback so others can learn from your experience!

avatar I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.

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