Cory catfish are one of the most popular fish in the aquarium hobby, but there’s a reasonable amount of misinformation available. 

Especially in the pet store, where they most likely just want to sell you stuff. Here is the full guide on which substrate is best for cory catfish – including my top picks.

In a hurry? Check my top picks

Flourite black sand is a natural, dark sand which makes cory catfish color up beautifully

The best sand for cory catfish

Super natural sand

This sand is a beginner friendly sand, which gives your tank a natural Amazonian look and feel

Fluval stratum

This rounded dark substrate is developed for planted tanks – with it’s natural feel ideal for cory catfish.

Best substrate for cory catfish

Cory catfish are one of the hardiest aquarium fish in the hobby, which is one of the reasons they’re so popular. When it comes to their gravel, many people often get it wrong though. So, what substrate do cory catfish prefer?

The best substrate for cory catfish is sand because cory catfish like to dig and rinse their gills with this fine substrate. In heavily planted tanks, a fine type of gravel is a better choice because plants do best on gravel. Unlike popular belief, sharp gravel will not cause barbel erosion and cory catfish can live on it, although not ideal.

Photo by naturalhistoryman on Flickr

Sand for cory catfish

Sand may be the best substrate for cory catfish, but not all types of sand are a good choice for cory catfish. Some types of sand tend to silt up causing no-oxygen zones which kill plants and cause a rotting bottom. There are also types of sand that have a lot of calcium in them, causing a pH spike.

This is why the choice of your sand isn’t as simple as some claim and you have to be careful picking the right type.

My favorite type of sand is flourite black sand. I always prefer dark substrates, although that’s a personal choice. Flourite black sand is also perfectly suitable for plants. Check it here on Amazon.

Photo by Thomas Siems on Flickr
  • It’s one of the cheapest substrates
  • Cory catfish love digging in it, displaying natural behavior.
  • A good type of sand is pH neutral
  • Sand has a larger surface area for beneficial bacteria
  • Because sand is so small, it can silt up
  • Although plants can do fine in sand, they prefer a slightly bigger grain
  • It’s harder to clean using a gravel vacuum

Some tips when picking out sand

  • When picking sand, look at the grain size. Take a sand that is at least  .7 mm or it will silt up very fast
  •  Try to find the origin or material from the sand. Some types of sand like play sand and coral sand have a lot of calcium and are sharp. 
  • Stay away from bright colors like flashy white or black, since it will stress out the cory catfish.
  • Maintain a +-1 inch thick layer of sand, to minimize the risk of the sand silting up.
  • Look at what plants do well in sand when picking this substrate. Read our guide for more.

Gravel for cory catfish

If you don’t like sand or if your other fish prefer gravel, this can be a good substrate for cory catfish, too. 

Cory catfish can be kept on gravel, but prefer a rounded grain that is around 1-3mm in grain size. With a sharp or big grain, cory catfish can’t dig freely. Although the effects of sharp gravel aren’t as severe as often said, a rounded gravel still is the best choice for their barbels.

  • It’s easier to vacuum clean than aquarium sand.
  • Plants prefer gravel
  • Gravel slits up less often
  • Cory catfish can dig freely in gravel
  • Gravel has less surface area than sand, and has less beneficial bacteria as a result.
  • Gravel is more likely to contain calcium rich pieces causing a higher pH

Types of gravel

Speeking of gravel, there are quite some types of gravel you can consider for cory catfish.


Aquasoils are very poular among more experienced aquarists, aquascapes and highly planted tanks. They’re considered more premium options, but they’re the best soil in most cases.

Aquasoils are often porous clay or vulcanic soils. They’re just small enough for cory catfish and the ideal size for plants to grow roots.


This is the biggest type of aquarium substrate. It can range from a couple millimeters in size to a couple centimeters. This type of substrate is less ideal for cory catfish and fish tanks in general. It provides less surface area for beneficial bacteria and plants have a hard time growing roots. Cory catfish also can’t dig in this substrate, because it’s too big and heavy.

Colored gravel

This type of gravel is painted. I wont be going into details, because you should never use this type of gravel. This substrate isn’t good for growing plants and the bright colors stress out the fish. 

Classic crushed stones

Although there’s no specific name for this type of gravel, it’s most comparable to a mix of small stones, a bigger version of sand. This type of gravel is quite small, but can be sharp for cory catfish.

Myth debunked: cory catfish barbels erosion

The popular belief regarding aquarium gravel with cory catfish is that is causes cory catfish barbels to erode and die off. 

This is a myth, and although cory catfish love playing in sand, sharp gravel isn’t the main cause of barbel erosion. Bad water quality or stress is. 

Photo by raneko on Flickr

As you can see, these C. panda, which is considered a more sensitive cory catfish species, have perfectly healthy barbels and are kept on big sharp gravel.

In fact, in many natural habitats, cory catfish live in streams where the substrate is a mixture of very sharp volcanic rocks, gravel and sand. It does have to be noticed that cory catfish can at any given moment migrate to another area where there is f.e. sand or leaves as a substrate. This isn’t the case in your tank.

This topic is controversial though, and some people swear by the negative effects of sharp gravel on their barbels.  

I’ll say that even though your cory catfish can do fine on sharp gravel, if you have the choice, why make it difficult for your cories? They certainly love sand or rounded substrates to dig and filter for food

Read the full guide on this website if you want to know more about cory catfish barbels.

What colour substrate is best for cory catfish?

  • Dark substrates – Matte black or dark brown are great colors. Many fish will color brighter on these substrates which makes them even more beautiful. Stay away from reflecting black or other bright dark colors. 
  • Light substrates – Light brown such as most sand types is also great and makes the tank look natural.

So, the best substrate colors are those who you could see in nature. Bright or painted substrates will stress out the fish and thus aren’t a good choice.

Bare bottom tank for Corydoras

Bare bottom tanks (tanks with no substrate) are especially popular amongst breeders. This is because this type of tank is easier to clean and the waste will be sucked up by the filter more easily. Ideal if you want cory catfish fry to grow fast.

Bare bottom tanks are also often used as breeding tank setups. These tanks often have to be quick to set up and easy to maintain (which also makes it easier to pick out the Corydoras’ eggs) so a bare bottom tank is a good choice. Read our full guide if you want to know more about breeding cory catfish.

A disadvantage of a bare bottom tank is that there will be less beneficial bacteria, since a big part of those live in the substrate. This makes a weaker biological ecosystem, which is less ideal in a long-term community tank.

Conclusion: bare-bottom tanks are great for breeding purposes, but less ideal for community tanks.

My three favorite substrates to buy

Now that we know what substrate types are the best for cory catfish, you probably want to know ‘but which one should I buy?’. No worries, I’ve listed my three favorites right here. All have their pros and cons, and for every situation there’s one that will suite you best.

Best overall substrate for cory catfish

My take

I have always been fond of darker substrates, in particular black. Many fish species including cory catfish color up the best on black substrate. This sand is just fine enough for cory catfish to dig around, but still bigger than normal sand which makes it ideal for aquarium plants.

Out of 10


At time of writing


  • Great for plants – This is substrate is a clay full of nutrients. Although this substrate isn’t #1 on my list for plants, it is great for plants that need some extra nutrients, such as Amazon swords (Echinodorus). As I pointed out, it’s also a bigger grain than sand, making it better for plant growth.
  • Ideal for bacteria growth, healthy ecosystem – This substrate is porous, providing lots of surface for bacterial growth. At the same time, it’s pH neutral.
  • Vibrant fish colors – On this black sand, the colors of your cory catfish will jump out more than on a pale color. 
  • Boosts natural behavior – The grain is slightly bigger than the second option on this list, but cory catfish still can dig freely.


  • The substrate comes in quite dusty – You’ll have to wash this sand thoroughly before putting it in the tank, or the water will be full of dirt.
  • The quality comes at a price – for beginners or people on a budget, the budget option on this list is a better option.

Best for breeding setups and most affordable

The best sand for cory catfish

My take

Natural sand always has been my go to substrate for most of my breeding tanks. It’s relatively cheap and gives a natural look to the tank (it’s practically the same as in the Amazon). If I’m on a budget but still search for a great substrate, this is my go to. 

Out of 10


At time of writing


  • A natural look – In the Amazon, cory catfish live on a mixture of sand and gravel, which is very similar to this sand
  • Boosts natural behavior – Because this sand is natural and very fine, cory catfish can dig freely: ideal for their barbel growth and natural behavior.
  • Biological balance – Sand has the largest surface area for bacterial growth, creating a better ecosystem inside your tank.
Photo by James Green


  • Silting up risk – In the Amazon, cory catfish live on a mixture of sand and gravel, which is very similar to this sand
  • Less ideal for plants – Because this sand is natural and very fine, cory catfish can dig freely: ideal for their barbel growth and natural behavior.

Best for planted tanks, a more premium option

My take

Fluval stratum is a substrate that’s developed especially for planted tanks. If you are big on aquascaping or have some plants that need special care, this is the go-to substrate. Again, it has a rounded small grain ideal for cory catfish. It’s a more premium (more expensive) option as opposed to the other two on this list, which is why I put it on place three.

Out of 10


At time of writing


  • Biological balance – This substrate is porous vulcanic soil, ideal for bacterial growth which improves the biological balance of your tank.
  • Healthy plant growth – This vulcanic soil is full of nutrients and has a quite big grain size, ideal for most plants. This substrate is quite light, so plants can loosen when first adding water to the tank. Making the substrate wet before filling the tank is the solution. 
  • Better water parameters for cory catfish – Cory catfish like slightly more acidic water (a lower pH) which this substrate helps to achieve. It will not crash the pH, but lower it slightly.


  • Only comes at a max weight of 8.8 lbs – It’s less ideal for bigger tanks. This makes it ideal for small tanks and small species like pygmy cory catfish
  • A bigger grain – Although not harmful, this bigger grain makes it less easy for cory catfish to dig freely and show natural behavior.
  • Comes in dusty – Just like most other aquasoils, this substrate needs to be washed thoroughly before usage.

Conclusion: the best substrate for cory catfish.

The best substrate for cory catfish is sand, primarily for people who are on a budget. Small grain gravel types are a great choice, too, especially because plants prefer these. 

In terms of color, always try to go for a natural looking substrate, as cory catfish and fish in general feel much better. On black substrates, the colors of cory catfish will pop out more as opposed to f.e. sand. Never buy artificially colored or painted substrates, these will stress out the fish!

It’s a myth that cory catfish barbels die off because of sharp gravel. This is mostly caused by bad water parameters. It stays controversial, though. Wo, I always give the advice to just pick a round or sand substrate, because why would you take the risk?

The three types of substrate I would recommend are: