Otocinclus catfish are popular because of how neat they look and how peaceful they are. These are stellar community tank fish that can work in many different types of tanks.
You might be curious about otos after hearing about them from friends. However, you might be worried about their size.
How big do otos get in a fish tank? Are there some otos that grow to be larger?
Read on to learn about how big otos grow. It’ll make it easier for you to choose the perfect otocinclus catfish for your aquarium.
How Big Do Otocinclus Grow?
Before going further, it’s important to understand that there are many different otocinclus catfish types. The most common type that you found being kept in aquariums are known as common otos.
Different otos are going to grow to different sizes. Below, you’ll learn a little bit about the various types of otos and how large they grow.
You’ll also get information about recommended tank sizes. This should help to see if certain otos will be appropriate for your fish tank or not.
Common Otocinclus Size
The common otocinclus catfish is the most common oto type that you’ll find. These are the fish that are usually sold in pet stores, but you can sometimes find other more exotic otos being sold.
A common otocinclus catfish will grow to be between one and a half inches long and two inches long. These fish are quite small, but they’re also known for being rather fast swimmers.
You need to keep at least six of these fish in the tank. They like to live in small groups of six or more and don’t do well in groups that are too small.
For this reason, you must have a 10-gallon fish tank or something larger for these fish. Many enthusiasts recommend going with a 20-gallon tank if possible.
Golden Otocinclus Size
Golden otos are very pretty and they’re sought-after because of how nice they look. They’re pretty much the same size as common otos, though.
These fish will grow to be around one and a half inches long at maturity. Some might grow to be just a little bit bigger than one and a half inches long, but it’ll be close.
Keep this fish in a 10-gallon fish tank or something bigger. It would be better to go with a 20-gallon tank, but you should be able to fit six golden otos in a 10-gallon tank if necessary.
It’s simply easier to go with a 20-gallon tank since you need room for rocks, plants, and decorations. Keep this in mind and go with the bigger tank if you can.
Giant Otocinclus Size
Giant otocinclus catfish grow to be a bit bigger than most. You likely expected that based on the name.
These fish grow to be four inches long on average. Some might grow to be 4.25 inches in a fish tank, but it depends on the diet as well as various genetic factors.
Since these fish are a bit bigger than average, you’ll need a larger fish tank for them. They do best in 30-gallon tanks or tanks that are even larger.
Remember to give these fish enough room to thrive in the tank. They need to be kept in groups of six or more like other otos.
Zebra Otocinclus Size
Zebra otos are much like other typical otos in that they don’t grow very large. It’s common for these fish to grow to one and a half inches long at maturity.
Some zebra otos have been known to grow to sizes of 1.7 inches long. Typically, the females are more likely to be larger than the males.
Ideally, you want to keep these fish in a 20-gallon fish tank. This is the best tank size to keep these fish comfortable and happy without overcrowding them.
Zebra otos can be a lot of fun to own. They look nice in community fish tanks because of how pretty their markings are.
Silver Otocinclus Size
Silver otos are small fish that don’t grow to be larger than two inches long. They’re much like the standard common otos in terms of size, but they look different.
These otos are known for having color patterns that look more silver than brown. It can be somewhat hard to tell them apart from common otos.
So you can see that there isn’t a huge difference between the two types of fish. These fish can also be kept in 10-gallon aquariums, but they do better in 20-gallon fish tanks.
Dwarf Otocinclus Size
Dwarf otocinclus catfish also stay around the same size as common otos. They won’t grow to be larger than two inches long.
These are another type of fish that can be hard to tell apart from common otos. This is because both fish have the same dark brown marking stripes.
The big difference is that dwarf otos have a blotch that can be found on their tails. Also, the brown stripe disappears by the time it reaches the caudal fin.
As you’d expect, the tank size requirements for these fish will be the same as common otos. They can be kept in 10-gallon fish tanks, but they do better in slightly larger 20-gallon aquariums.
Otocinclus Max Size
The max size of an otocinclus fish will change based on the type that you buy. If you buy a common otocinclus catfish, expect it to grow to be two inches long.
Smallest Otocinclus
Dwarf otos are the smallest otocinclus catfish that you will see being sold. They aren’t that much smaller than common otos, though.
Many dwarf otos will grow to be just one and a half inches long. Although they aren’t big, they still need to be kept in tanks that are sizable enough.
Commonly, these fish are kept in 10-gallon tanks or 15-gallon tanks. Most say that 20-gallon tanks are the best for them, but you might want to go bigger if you plan to keep them in community aquariums.
These fish must be kept in groups of six or more. They’re peaceful fish that can add a lot to your aquarium.
How Fast Do Otocinclus Grow?
Many otocinclus catfish grow rather fast. These fish can grow rapidly if they’re kept in ideal conditions.
It’s best to keep the conditions in the tank perfect to allow the fish to grow strong. These fish need the water to stay very clean so they can remain healthy.
This means regular tank maintenance and consistent weekly water changes. Ensuring that the fish have enough food to eat is imperative, too.
When otos have plenty of algae to eat and you’re supplementing their diet with algae wafers and blanched veggies, they’ll grow fast. It’s said that many otos can reach maturity in as fast as three to four months.
However, it’s common for otos to reach full size after one year of growth. The fish could grow to its maximum size in anywhere from four months to one year.
Are Otos Peaceful?
Yes, otos are very peaceful fish. They are known for being shy and wanting to hide rather than fight.
This makes them good community tank fish, but you have to pick tank mates carefully. Since these fish are usually pretty small, they can easily get bullied by more aggressive fish.
You need to pick fish that will leave them alone. Also, you have to pick fish that aren’t big enough to eat the poor otos.
Even so, these fish make great community fish tank members. They’re fun to observe and they can help to keep the tank clean.
Are Otos Good Cleaners?
Otos are considered to be good cleaning fish. You can put them in a community fish tank and they will eat algae, bacteria, and other debris in the tank.
This doesn’t mean that you won’t have to clean the tank yourself, though. It just helps to keep algae under control.
Keeping a group of six or more otos in a tank can really make a difference. These are among the most popular types of catfish that people buy for cleaning purposes.
Final Thoughts
Otocinclus catfish aren’t very big at all. There are giant otos that grow to be four inches long or slightly larger, though.
Otherwise, most otos grow to be two inches long at most. They are small fish that can fit in relatively small fish tanks.
They must be kept in appropriately-sized groups to thrive in aquariums. You’re not supposed to keep fewer than six of them in one fish tank.
If you want to keep ten or more of these fish in the same tank, you’ll need a larger tank than the minimum recommended size. Also, when keeping these fish in a community fish tank it’s best for the tank to be rather spacious.
Remember to monitor the water parameters carefully when caring for these fish. They need the tank to stay clean because they can suffer if the oxygen levels dip.
Do your best to care for the otos and they will live in your tank happily for years. These fish are sure to be excellent additions to your tank whether you’re keeping them in a community tank or caring for them in their own aquarium.
Jeff has always enjoyed having pets, but as a child, he was drawn to his family’s fish tank. Being able to maintain a small ecosystem and observe the behaviors and interactions in the underwater world peaked his interest early on and has kept him hooked until this day. On Avid Aquarist, Jeff shares everything he’s learned about helping aquatic life survive and thrive in a home aquarium.