Can Janitor Catfish Live with Koi? (Solved & Explained!)

While janitor catfish can live alongside koi in theory, I’ve read quite a bit from people who’ve had bad experiences mixing them. You need to make sure that you have enough space for all the fish of both species to stay safe and apart from one another.

It’s not unheard of for janitor catfish to approach 28 inches in length, which makes them larger than some varieties of koi. Experts on pond maintenance often recommend that you have upwards of 500 gallons for each fish you have.

So can janitor catfish live with koi? Yes if they are the same size as the koi and each fish at full size has 50-100 gallons of space. No, if the catfish or koi are much bigger than the other when you introduce them together.

Will Koi Eat Them?

Mature koi usually won’t try to eat janitor catfish, but I’ve heard plenty of stories where an aggressive koi will certainly start to pick on a more passive cat. It depends somewhat on the temperament of both the koi and the catfish in question.

Granted, if you’re not feeding your koi they might start to look at anything as food! That’s a great way to make them pick fights, so it’s a good idea to get on a healthy feeding schedule going as soon as you introduce any fish into your water.

Will the Catfish Eat My Koi?

As their name suggests, janitor catfish are supposed to be scavengers. However, they can get fairly large and if they do they might actually try to eat smaller koi especially if they’re immature.

That being said, janitor catfish might be a slightly better pick than other species. I’ve heard horror stories of full-sized five-foot channel cats that could swallow smaller koi fish whole!

Even relatively small janitors will potentially eat immature koi. That being said, they may not even interact at all with your koi if there’s enough space to keep all of them happy.

List of Catfish that can Live with Koi

Fortunately, there are some really good choices if you want a catfish that will cooperate with your koi fish:

  • Columbian Shark
  • Iridescent Shark
  • Bumblebee Catfish
  • Bandit Cory

Some of these names threw me off at first, especially considering that two of them include the word shark! That being said, all four are catfish species and they should all have a pretty wide temperature range at least as far as these kinds of fish go.

Though these four are usually considered to be better choices, you’ll still only want to keep them alongside more mature fish to avoid any unfortunate situations. After all, even the friendliest fish might look at their smaller neighbors as a snack!

How to Stop Koi and the Other Fish from Fighting

Poor quality food or not enough of it can start fights between your koi and cats, but overstocking is probably the biggest cause of problems.

Make sure there’s enough space for all of your fish. You’ll need to consider the fact that they might grow much larger than you imagine.

Different breeds might fight more than others. If you notice that one of your koi seems to be more aggressive, then you might not want to introduce janitor catfish into the mix before you know more about their temperament.

How Big Will They Get?

Average koi fish grow between 20 inches and a foot in length. They can weigh up to 12 pounds, depending on the specific breed you have.

A few pet supply places I’ve looked into have said that Butterfly and Jumbo koi tend to be much larger than most. Butterfly koi in particular tend to be passive and their large fins might be an attractive treat for good-sized catfish.

You may want to look into domestic koi if you’re trying to keep space constraints down since they usually don’t get much bigger than a foot or so.

What Should I Feed Them?

Take a look at the labels on food geared for koi and catfish. You’ll probably notice the same thing I did: that their eating habits are actually pretty close.

In general, a flaky floating food that offers more than 30 percent protein is a good pick. When it gets colder, you’ll want to go with food that sinks deeper.

Since extra protein normally doesn’t harm fish, you could try higher protein concentrates too. Anything over 40 percent or so would be too rich, however.

How Often to Feed Your Fish

Mature fish should be fed around 4-6 times every week, assuming that the weather is warm enough for your fish to eat regularly. As temperatures drop, you’ll probably notice your koi and catfish eat much less.

According to most feeding instructions I’ve come across, you’ll need to feed hatchlings more often. Don’t overfeed, though, because too much food can kill an otherwise healthy fish.

How Long and Deep Should the Pond Be?

Pretty much everything I’ve researched online recommends ponds to be no smaller than 7×8 feet and around four or five feet deep. This makes for a pond that holds around 1,500 gallons of water.

Both koi and cats grow pretty quickly, so they’re going to need more space as time goes on. This might sound huge, but you’re going to need it to be decent-sized as they grow larger.

How To Help Them Through Winter

Start slowing down the amount of food you give your fish once they start consuming less. Marine veterinarians, I’ve followed an online claim that koi shouldn’t eat much of anything once the temperature drops below 50°F or so and stays there for several days.

You might live in an area that encourages the growth of ice on the top of your pond. If that’s the case, then you don’t want to panic like I did the first time I saw this.

Chances are that the ice is actually helping to regulate the pond as your koi and catfish both go into hibernation. When the ice starts to get a bit thicker, aerate the top of it to help them breathe.