Recommended Substrate For Otocinclus? {Gravel Vs. Sand}

The battle for sand vs. gravel substrates rages on!

Should we call off the debates with a definitive answer for the best substrate for your Otocinclus? In this article, we’ll try to settle the argument once and for all.

Should I Use Sand For Otocinclus?

A sandy substrate is your safest bet when it comes to the bodies of your Otocinclus. They do not have protruding barbels like corydora catfish.

If you keep both species together in the same tank, use sand to protect the barbels of your cories. Otherwise, your Otocinclus are happy with smooth gravel, rocks, dirt or sand.

Provide the plants for much needed oxygenation and hiding spaces. Make sure the sandy substrate is suitable for the plants you choose. Place caves, rocks, decorations or driftwood on the substrate for your Otocinclus to enjoy grazing for algae and diatoms.

Do Otocinclus Spend Most of Their Time On The Substrate?

Although Otocinclus stay near the bottom of your tank, they are not necessarily scavengers. Most of the leftovers, flakes, pellets and other debris in the substrate do not interest your Otocinclus as much as algae does.

Look for them to prefer:

  • driftwood
  • rocks
  • plants
  • caves
  • decorations
  • glass

The areas above will contain more algae or diatoms for your Otocinclus. The substrate should be smooth enough without sharp rocks that could harm these scaleless catfish, but don’t expect them to remain there throughout the day. They have work to do cleaning other surfaces!

Do Otocinclus Dig Through The Substrate?

Your Otocinclus will most likely prefer to graze, suck and clean off algae or pick away at vegetables or plants instead of digging through the substrate.

Otocinclus will be more inclined to rummage the substrate if they are trained to eat what you give them. The food will sink or you will secure it to the substrate for your Otocinclus to enjoy. This will be the most common time when these catfish interact with the substrate.

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What Is The Best Substrate For Otocinclus?

We are not going to lay the law and command that one particular substrate is the best over the others. We don’t want any Otocinclus to get their scaleless bodies scratched or cut on a sharp substrate, but the rest is up to you.

This is our favorite method of a blended substrate for our Otocinclus:

  • Buy organic garden soil.
  • Wet and let dry to mineralize it. 
  • Pour 1 inch of soil into the tank. 
  • Add 1 inch of fine gravel or sand above it. 
  • Put in plants that grow fast. 

The soil mixes well with fine gravel or sand to create a natural setting for your Otocinclus to thrive. There are many other methods that you may use. We would love to hear from you. Email us with your thoughts!

Will Otocinclus Eat From The Sand?

The sand is not a natural place for algae to grow. Your Otocinclus would rather search other surfaces and remain impartial to digging the sand for nutrients. They will swim low, but won’t dig the way corydoras do.

Both types of catfish will not ingest sand into their digestive systems. They may suck some in, but are able to expel it from their gills and mouths. A cory catfish will do this more often. An Otocinclus will leave the sand alone for the most part.

What Other Substrates Work For Otocinclus?

You can create your own blend of substrate for your Otocinclus as long as nothing in there is sharp. Consider the following:

  • flat marbles
  • smooth river rocks
  • different sizes of gravel
  • crushed stones
  • sand and soil
  • gravel and soil 
  • decorative substrates

You can get creative with this if you like. Your Otocinclus will not mind. Add colors, smooth textures and designs. Allow for rocks to be included to promote more spaces for algae growth.

Should I Put Plants In The Substrate For My Otocinclus?

Your Otocinclus will not eat your plants. Occasional nibbles will take place, but their real effort will be spent on discovering and devouring any algae that forms on them. The following plants will help Otos create natural feeding sites with comfort, grazing and hiding as they see fit:

  • Anubias
  • Java Fern
  • Echinodorus
  • Cabomba 

What Is The Otocinclus’ Substrate In The Wild?

Otocinclus swim in huge shoals of hundreds or thousands. They prefer shallow streams and rivers. This is because the sunlight can directly reach the substrate and rocks to ignite more algae growth.

Algae is the primary food source. The substrate comes secondary. The South American rivers, basins and streams where they come from are mostly muddy.

We tend to avoid mud as our substrate of choice for obvious reasons. Expect a mixture of sand or gravel to work well for your Otocinclus, but pay more attention to the needs of your plants and other bottom-dwellers.


There shouldn’t be a debate on the best substrate for your Otocinclus. They are fine with your choice of fine gravel or sand and many other blended substrates in between.

They will stay close to the substrate, but will not be found digging, scraping or rubbing through it if they are healthy and well fed. Keep the substrate smooth and be sure to add plants, rocks, caves and decorations for your Otocinclus to continue its hunt for algae.


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Brian Arial

Brian Arial has kept fish for leisure and worked with fish stores for most of his life. He enjoys writing and caring for aquariums and ponds.