What is a Dither Fish?

Dither fish are a good concept for the new aquarist to grasp, especially as you begin to move into keeping multiple species together. They can provide valuable security for other fish in the tank, in a rather counterintuitive fashion.

So, let’s dive in and I’ll explain what dither fish are, help you figure out if you need them, and then we’ll make sure you pick the right fish for your tank’s needs!

tiger barb


What is a Dither Fish?

Dither fish are fish that will get out in the open and help convince other fish the aquarium is safe. You usually do this by picking a schooling species of the appropriate size and adding them to the tank. After all, if schools of fish are forming then others may realize there are no predators in the immediate area.

Dither fish are usually used to convince shy fish to come out from hiding, but they can also be used to generate more natural behavior in some aggressive fish.

People often forget that while we just see fish as “just” fish, they actually have a very wide range of behavior, intelligence levels, and needs. 

Remember, mice, lions, and elephants are all part of the same class as us. Fish are just as complex in their differences. A more intelligent fish will look around the tank and observe the behavior of other fish in order to determine how to proceed, especially when introduced into a new environment.

If nobody’s out there, it’s a red flag. Smaller fish flee when larger predators come in, and overly still waters are a sign that something is wrong in their natural environment. So we insert dither fish to convince our more intelligent and shy critters that it’s okay to come out.

Think of it like walking into a completely empty store. You’ll be a bit confused, a bit wary, and not sure what’s going on. If the store had the normal workers and customers you wouldn’t give the environment a second thought. 

Dither fish are just the folks that fill up the store and let you know that nothing is amiss.

But not every tank needs them, so how do you know if you do?

Do I Need Dither Fish?

Dither fish are mainly used in cichlid tanks, but they can be helpful for a lot of shy creatures. I’ve used them with Tire Track Eels, for instance, to get them to come out more during the day. Shy fish and fish that seem nervous leaving their little spot in the aquarium will usually benefit.

I’ll usually include a school of Zebra Danio when setting up a tank, for instance. They’re very fast, and the school usually lasts for some time.

To some extent, every fish in a tank acts as a dither fish. But we’re usually talking about a school specifically for that purpose. In a community tank, for instance, there is rarely a need for a specific school of dither fish. There are still some circumstances (ie: lots of oddballs) where they can help but they’re mainly used with cichlids in practice.

Dither fish aren’t meant to pick up extra aggression from a specimen that likes to fight. The fish used for that purpose are generally called “target fish” and they’re a slightly different subject.

In general, cichlid tanks and any tank that has very shy fish will benefit from a school of dither fish. Just make sure that you can fit them into the tank’s bioload.

They’re even useful in peaceful community tanks, adding some security for most inhabitants.

One place where dither fish can be used that seems a bit counterintuitive is breeding pairs of aggressive fish. It helps to make the bond between the mating fish a little bit more stable since they’ll have an outside target for their aggression. 

It’s not required, but if you have a pair of cichlids that are getting too rough with each other during mating then you can try adding some sort of dither to the tank. Target fish are also used in these circumstances, especially if the tank is large enough for there to be more than one claimed territory.

A lot of working with finding the right dither fish will just come with experience. Fish like cichlids are often variable in personality, much moreso than things like Guppies, so the animal in question is also a large variable.

In general, look for the following signs:

  • Are any fish acting overly shy?
  • Do your fish spend a lot of time hiding instead of swimming openly?
  • Is your fish becoming overly territorial?

If any of the above are true then you may want to add some dither fish into the mix.

How to Pick and Use Dither Fish

The biggest factor in picking a good dither fish is whether or not they’re shy when schooling. While some fish will begin to break up their school and try retreating into the hardscape, others will simply keep going.

You need a sizable school. While they’re not meant to soak up aggression, they’ll end up being chased sooner or later in a cichlid tank.

That also means that you’ll need enough room for them to get away from any aggressive fish. Bigger schools make it harder for aggressive fish to single out any single member of the school.

So what you’re looking for is a bold schooling fish in the appropriate size for the tank and other inhabitants.

There are a lot of different fish out there that are suitable, but the above should be your primary consideration.

Size matters a lot as well. A good dither fish will be just a bit too big to make a meal for predators in the tank, while remaining the right size to have room in the tank itself.

Dither Fish for Small Tanks (≤30 gallons)

In this size of tank you’ll be limited in your options, especially since you still have to deal with the bioload of both the dithers and your other fish.

I’d recommend going with one of the following:

  • Zebra Danio- The classic small dither fish. Zebras are incredibly fast, fearless, and readily available. They may move a bit too fast for some very shy species, but they’re my pick if you don’t have a specific species in mind.
  • Cory Catfish- Corydoras catfish actually work quite well as dithers for smaller tanks. They’re active, armored, and rather quick. Most cichlids will just ignore them, but their presence means safety.
  • Neon Tetra Often used in small tanks and with Angelfish or Discus in larger tanks. Cardinals also work well for this task, and are slightly larger.
  • Livebearers- Guppies, Mollies, and other livebearers are great for small, shy cichlids like German Rams but they’re a bit small to use as a dither for most species. They also tend to be a bit less evasive, so attrition can become a problem.

For the most part, small tanks are going to be limited ot one or two specimens plus the dither fish you choose. For that reason, small and colorful Tetra are often chosen to serve this role for aesthetic reasons rather than practical considerations.

In all honesty, anywhere under 30 gallons bioload is going to be the largest factor in your choice. Fit what you can, just make sure that you have at least 6 fish in the school.

Dither Fish for Medium Tanks (30-125 Gallons)

Once you get over 55 gallons or so, things start to really open up for your dither fish options. As always, you need to balance the bioload of your larger fish with your dither fish but if that’s taken care of? There are a lot of great options.

The following are often used:

  • Giant Danio- Giant Danios are one of the most common dither fish for use with larger cichlids. They’re incredibly fast, large enough to not be eaten by most cichlids, and very confident swimmers.
  • Tiger Barbs- A bit smaller, but much feistier, Tiger Barbs make a good choice for tanks with smaller cichlids. They’re usually able to defend themselves, but some of the larger cichlid varieties can make short work of them.
  • Sailfin Mollies- Sailfin Mollies get a bit bigger than the other species, which makes them a good choice for medium sized tanks.
  • Rainbowfish- A solid option for larger fish that may be able to damage smaller dithers. Just pick your species carefully and make sure there’s enough room for everyone to be happy.

Medium sized tanks often have the biggest range of available fish. While larger tanks have more potential, the only fish that are often kept in these larger enclosures which use smaller dithers are Discus.

The key here is the same as anywhere else: fast, schooling, and sized for the fauna in your tank. 

Large Tanks (>125 Gallons)

In the largest tanks, you have a lot of potential options. If you’re keeping some of the larger cichlids and other species, however, then you need dithers that can compete.

There are two main fish that are great to use with larger, aggressive fish:

  • Tinfoil Barb- Their speed, tight schooling, and fearlessness make Tinfoil Barbs ideal dither fish. The only issue is their size, since they reach over 12” in length by the time they’re full grown so they require a ton of space.
  • Silver Dollar- A bit smaller, coming in at around 6”, Silver Dollars are another great fish for larger tanks. Be careful with any sort of planted tank, however, as Silver Dollars are voracious eaters of vegetation.
  • Pacu- For tanks of over 300 gallons, a school of Pacu make great dithers. They’re also fascinating fish in their own right, but try to avoid getting “nipped” with their hard, human-like teeth.

Options are pretty much endless as tank sizes grow from large to truly massive.

The above fish are just examples, possibilities seriously open up when you have the space to add schools of fish that are over a foot long.

What About Target Fish?

I briefly mentioned target fish above, but they’re another good thing to be aware of. In particular, cichlid keepers will often want to have target fish available.

The goal of a target fish is simple: they’re used to channel aggression in a different direction. Because of their specialized use, you’ll find that it’s not quite as simple as picking a simple school of fish.

Schools can still be used as target fish, especially for mating pairs of cichlids. A school of Zebra Danio, for instance, will often make it much easier to breed smaller cichlids like Convicts. Their presence gives the couple a mutual outlet for their defensive aggression, making it less likely they’ll mess with each other.

Other times, a small cichlid added in a tank large enough that territories don’t overlap, can be used in the same way. People will also use fast fish that stay in the rocks, but you need 2-3 of them to keep the aggressive animal from cornering just one of them.

Target fish are not supposed to “take a beating.” Instead, they’re used to draw off some of the aggressive instincts of the other animals. If the fish is regularly being damaged, you need to change strategies and find another way to manage the aggression of the fish in question.

Target fish are a more complex subject than dithers and they’ll depend a lot on the individual animals you’re keeping. Experimentation is the key to finding the right mix, and it can make things like breeding cichlids easier to manage when done correctly.

Active Water, Happy Home

Dither fish are one of the more complex aspects of the hobby, as there is no correct answer to the problem they solve. Instead, learning what a dither fish is, and how to use them, is a natural part of learning to keep both shy and aggressive species. Just knowing the concept gets you one step ahead.

What is a dither fish? You know now, the only thing to do is proceed with finding the right ones for your tank!