Can Corydoras Live Without Sand?
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It’s well known that Corydoras are bottom dwellers that take pleasure in patrolling their habitat’s lower regions.
They also bury themselves in the sand often and perform sand sifting, which is a feeding technique specific to catfish and other bottom feeders.
But can the fish survive without sand, or is this form of substrate paramount to their survival? Let’s look into it!
Do Corydoras Need Sand?
Yes, Corydoras need sand. This isn’t optional but required for them.
There are several reasons for that, primarily:
- Hiding – Corydoras are peaceful and timid fish, so they don’t have any means to deter predators or fight with other fish. Housing them with more aggressive or curious fish that bother them frequently can increase their stress levels. To escape the unpleasant situation, Corydoras often bury themselves in the sand as it provides them with a plus of security and comfort.
- Feeding – There are 2 points to mention in this sense. On the one hand, Corydoras collect any visible food resting on the substrate, as sand is fine and compact enough to keep everything at the surface. These are useful features to have when feeding your Corydoras sinking pellets or live food that could sink in gravel. On the other hand, Corydoras perform what’s known as sand sifting. In short, they take mouthfuls of sand, keep whatever organic matter they can eat, and eject the sand via their gills. This critical feeding behavior shows why Corydoras can only live in sandy areas.
- Comfort – Maybe you can keep your Corydoras in aquariums with different substrates, including bare-bottom setups. But the fish won’t be as comfortable as it would be with a sand substrate. That’s because the fish’s natural habitat is all sand and your goal should be to emulate those natural conditions for a plus of comfort and safety.
So, sand really isn’t an option, it’s the only option. But more on that shortly.
How Much Sand do Corydoras Need?
The thickness of the sand substrate depends on the fish’s size and behavior. Not all Corydoras are as aggressive diggers as others, but they all like to dig in search of food.
Aim for a substrate thickness of approximately 1.5-2.5 inches at most. This is enough to provide the fish with all the sand they need to perform their daily activities.
Corydoras won’t dig in more than that. Most will only go approximately 1-1.3 inches into the substrate, depending on the fish’s size.
What Sand is Best for Corydoras?
If we’re talking about the vast majority of Corydoras, go for extra fine silica sand. This is their best option, given the catfish’s evolutionary features.
Corydoras have sensitive mouths and barbels that they use to scan the sand in search of food. They also exhibit sand-sifting behavior, which is only safe with fine-grained sand like silica.
Anything other than that can cause the catfish to experience mouth and gill traumas, opening the door to infections and even death.
It’s why you can’t use gravel or a combination of sand and gravel in a Corydoras tank.
Pygmy Corydoras are the exception here since these are open-water swimmers that don’t rely on the substrate as much. A bunch of live plants and some hiding areas are enough to keep these ones happy and calm.
Can Corydoras Live in Bare Bottom Tank?
Yes, they can because these fish are adaptable and hardy, but I would not advise it.
Corydoras can get stressed when kept in improper tanks that are so far apart from their natural dwelling habitats. The reason for that is the fish’s evolutionary predetermination.
Whether there is sand in the tank or not, the fish will exhibit the same feeding and hiding behavior. It will instinctively go towards the bottom to seek shelter and food on the substrate.
If it can’t, the fish will exhibit signs of stress which can be fatal. Even specimens adapting to the changes experience a lower quality of life and shorter lifespans than those enjoying a natural-looking setup with a sand substrate.
So, if you want what’s best for your Corydoras, go for fine silica sand.
Can You Keep Corydoras on Gravel?
No, you can’t, and you shouldn’t try it, either. Corydoras feed on the sand, and they exhibit frequent burying behavior.
The gravel is too large-grained for their liking and can hurt their skin and gills. It can also become deadly due to the fish attempting to sift it, and they will.
It’s common for catfishes to choke on gravel particles, many of which weren’t large at all.
The same can occur in a mixed substrate with a combination of sand and gravel.
You should always provide your catfish with a fine and carefully-selected sand substrate devoid of shards, pebbles, or other large particles that could become an environmental hazard.
Sand is also great for your tank as a whole for several reasons, such as:
- Easy to clean – You only need to vacuum it regularly to keep it in a good condition. It also doesn’t hurt that fish waste and other residues remain on the surface due to the sand’s more compact nature.
- Better feeding opportunities – Sand is always better for community setups with cleaning fish like Corydoras. All food residues sinking to the bottom remain on top, allowing scavengers to find them easier.
- It looks nice – There’s no denying that sand is great due to its aquascaping potential and its esthetic effects.
To note a handful of problems:
- Anaerobic pockets – These are sand-specific problems that consist of pockets of air forming under the substrate where ammonia-producing bacteria thrive. These pockets fill up with ammonia and, when disturbed, release it into the environment. Anaerobic pockets are often deadly, as you may suspect, which makes having a good prevention mechanism in place essential. Stirring the substrate and vacuuming it regularly will prevent the formation of anaerobic pockets.
- Not plant-friendly – Sand is an inert substrate that doesn’t offer good anchoring opportunities for rooted plants and has no nutritional value. So, rooted plants require root tabs to survive in sand. You will need to replace root tabs weekly or even several days apart, depending on the plant’s type, size, and growth rate.
- Anti-filtration effect – Every aquatic setup requires a good filtration system, but the circumstances are trickier when sand is involved. Bottom dwellers that tend to disturb the sand often can become a liability due to the sand particles being sucked in by the filtration system. This can decrease the filter’s effectiveness over time and even clog the media.
If you can work around these issues, sand will make a perfect addition to your tank.
Not to mention, it’s absolutely necessary for a Corydoras environment, so, ultimately, you need to circumvent these issues anyway.
Corydoras can live without sand, but they will live pitiful and sad lives.
If you want what’s best for your catfish, invest in a good, extra-fine silica sand substrate to mimic their natural environment.