how fast do jack dempseys grow

How Fast Do Jack Dempseys Grow?


If you are thinking of adding Jack Dempseys to your fish tank, it’s important to know how fast these fish grow and how big they will get. This will allow you to determine whether they are a suitable addition to the tank or not.

Although the environment can affect growth rates, Jack Dempseys tend to grow quickly, and could gain as much as 3 inches in around 6 months, or even more. They are big, aggressive fish that get to around 6 inches long by the time they are a year old.

Let’s look more at the growth rate of a Jack Dempsey and find out what these fish need and how you can keep them. This will maximize your chances of success with this tricky species.

How Big Is A Full Grown Jack Dempsey?

Jack Dempseys are large fish, and many people don’t realize this before they purchase one – which can cause major problems if the aquarium is not big enough. In the wild, a Jack Dempsey male can reach around 12 inches or even more, while in captivity, they will usually grow to approximately 10 inches.

Wild females will reach around 10 inches in the wild, and about 8 in captivity. If the tank that the fish are kept in is noticeably too small, they probably won’t get as big, so your Jack Dempsey might only reach 6 to 8 inches, or possibly even less.

However, they will be miserable if they are kept in crowded conditions, so this isn’t a good way to keep your Jack Dempsey small.

Overall, a full grown Jack Dempsey is a large fish that needs a large aquarium. They may start out small, but they can grow around half an inch per month, and reach their full size within a few years. Even a juvenile Jack Dempsey may be pretty large, thanks to the quick growth rate.

You should also be aware that because Jack Dempseys can get so big, they will eat other tank inhabitants given the chance. You need to make sure that you house them with compatible species if you want your other fish to survive.

Can 2 Jack Dempseys Live Together?

As we have already noted, Jack Dempseys are aggressive fish and that means you need to use caution if you are going to house two in the same tank. You might be wondering if this can even be done or if they will attack and kill each other.

The answer is that it can usually be done, but it isn’t easy, and you need to pay close attention to your setup and make sure that the fish have sufficient space, so that they can keep away from each other and feel as though they have some territory within the tank. The smaller of the two is likely to avoid the bigger one.

You should also provide your fish with some hiding spots, and put in some foliage so that they are not always in each other’s line of sight. Some Jack Dempseys will do better together than others, but in general, it is possible to keep 2 of these fish, provided that you do not overcrowd them. If they can get away from each other, they will normally coexist peacefully.

It is worth noting that most people consider Jack Dempseys an advanced species, so if you are a beginner, it’s best not to keep 2 or more together.

What Size Tank Do Jack Dempseys Need?

One of the most important things about keeping Jack Dempseys is making sure that they have enough space. It is all too easy to buy one of these fish when it is still small, add it to a small aquarium, and then find that it quickly outgrows the space and ends up in unsuitable, cramped conditions.

If you are going to keep one of these fish, you need to make sure that you give it sufficient amounts of space. Opt for a 60 gallon aquarium at least when your fish reaches its adult size. This will just about give the fish enough room, but it isn’t ideal, and a bigger space would be better.

The more space your fish has, the happier it will be, so if your setup space is limited, you should avoid keeping a species like the Jack Dempsey. Go for smaller cichlids that don’t need as much room.

If you are keeping two Jack Dempseys, you will need a larger tank, and something like 100 gallons is the minimum that they can live in. If you house them in a smaller enclosure, they are likely to get stressed out, extra aggressive, and possibly even sick.

If you don’t have enough room for this sort of aquarium, you’ll need to choose an alternative species of fish because Jack Dempseys need sufficient space if they are to thrive.

How Many Jack Dempseys Should Be Kept Together?

You can keep multiple Jack Dempseys in an aquarium if you choose to, but you must make sure it is large enough for them, and many people advise having only one male per tank. The personalities of these fish can vary quite a lot so it is possible to make other setups work sometimes, but choosing one male is the safest option.

If you are going to keep a group of Jack Dempseys, you will need a very large aquarium. Use 50 to 60 gallons as a rule of thumb for each fish. In general, people don’t keep more than 3 adult Jack Dempseys together, and this would require around 150 gallons at least.

Giving the fish sufficient space will help to minimize aggression and make sure they stay happy in the aquarium. If you aren’t able to do this, you should avoid keeping several Jack Dempseys, as they are likely to harm each other or get stressed by the overcrowding.


Jack Dempseys can grow surprisingly fast when their conditions are good, and may gain up to 6 or even 7 inches in a year. Because of their fast growth rate and large adult size, they need a suitable tank that gives them ample swimming room, especially if you are going to keep several of these individuals together.