Least Killifish 5 Gallon: Top Features You Should Know

Do people often wonder if they can hold at least killifish 5 gallon in an aquarium? And the answer is “YES”.

The majority of the time, despite having a very intimidating name, these fish are actually quite peaceful, even though they have a mean-sounding name. 

I have seen isolated instances of male killifish displaying aggressive behavior towards other male killifish, but that is it. It is evident that these fish have a lot of colors.

The question is often posed as to how many killifish can be comfortably housed in a tank of five gallons? In order to fit two Killifish in a 5-gallon tank, you should be able to provide at least 2 gallons of space for each fish. 

There is a risk that they will attack the other males if you ever keep more than one in your tank.

In the following paragraphs, we will be discussing in greater detail the size and requirements of a kill fish tank.

If you have a large enough aquarium, you can technically house as many killifish as you wish, so long as you are keeping them in a single aquarium. 

How Many Killifish Can You Have In Tank?

In light of this fact, it is essential to note that male killifish can be quite aggressive towards other male killifish, especially during the breeding season and if they don’t have the proper space to live comfortably.

Thus, if you are looking at keeping multiple killifish together, such as having four of them, only one should be a male.

You should be able to avoid problems with aggression by observing the 3 to 1 female to male ratio, particularly if you follow the rule of 2 gallons of water per fish discussed above.

What Is The Need For Killifish To Be In Pairs?

In terms of their biological criteria, Killifish are not considered to be schooling fish, so if necessary, they can be kept alone.

There is however something about them that they seem to enjoy having some of their own species around, both as a display of company and also because, in nature, safety is found in numbers.

In order to ensure that the killifish do not get crowded, it is strongly recommended that you get at least 3 or 4 fish and keep them together. 

Having tank mates of the same species will make them much happier, as they will feel closer to one another.

Accommodations For Killifish

Before looking at whether you should buy yourself some killifish right now, there are a couple of things that you should be aware of before you roll out and get some of them. Let’s look at those now.

Temperament Of The Water

Subtropical fish are best kept in waters that are about moderately warm. They don’t want to remain in sweltering water for too long.

You should keep in mind that the exact temperature of the water depends on what kind of killifish you have.

In general, it is advisable to keep killer fish in a range of 68 to 75 degrees Fahrenheit. It is said that the majority of killifish are able to survive in 72 degrees water without suffering.

This means, based on all probability, that you will need a decent aquarium heater, in addition to an aquarium thermometer with which to gauge the temperature in the aquarium.

Intensity Of Water

I have to reiterate that the exact type of killifish that you use will determine what kind of water you need.

The fish prefer water that is normally quite soft, with a dGH reading that does not exceed 10 or even go below 7. In most cases, however, as long as the pH values are at least 7.

It is a very hardy fish, so it is important to keep the water’s hardness level within these parameters at all times, to make sure that you have a happy killifish.

If you are unsure of the type of account you have, make sure you do some research. In some cases, water conditioners may be necessary for you to use.

Least killifish prefers normally quite soft water
Least killifish prefers normally quite soft water

A Water’s pH Value

It is also important to keep in mind that the pH and acidity of the water needed for killifish will depend on their specific type of fish, just like with the temperature and hardness of the water.

On the other hand, these fish tend to prefer water that has a pH level of anywhere between 6.0 and 7.0. Therefore, for the majority of them, water that is slightly acidic is the most suitable.

Firstly, you will have to do some research about the exact type of killifish you have. Secondly, it is recommended to get yourself an aquarium pH testing kit to enable you to determine the exact pH level of your aquarium.

Reverse Osmosis & Filtration

A good deal of dissolved oxygen in the water is what is usually preferred by killifish when it comes to aeration. A small tank may need a small air pump or airstone in order to make sure that your tank is properly airtight.  

In addition, these fish have quite delicate requirements regarding the quality and cleanliness of the water, or in other words, they need the water to be quite clean in order to survive.

In order to obtain the best results from your water filtration system, it is imperative that you look for a good filter that covers all three types of filtration. These include mechanical, biological, and chemical filtration.

For a killerfish tank that holds 10 gallons of water, you will need an aquarium filter that can handle roughly 30 gallons of water every hour, according to aquarium recommendations.

Although these fish are well adapted to living in the waters of coastal areas, you must keep in mind that they do not like strong currents.

Hence, it would be wise to install a back-trickle or waterfall filter there, such as a hook-on. This keeps water flowing in the tank at a minimum and can also assist in aerating the body of water at the same time.


As a rule, killifish don’t do very well in bright lights. It is actually more likely that they are more comfortable in a very dark and dim environment. 

The environment shouldn’t be too dark, or too bright both of which are harmful to the sight.

There is no need to purchase special aquarium lights for these fish, a standard, low power aquarium light will do just fine.


In terms of a substrate, you need to use a combination of peat moss and sand in order to get the greatest results from your aquarium with killifish.

There are many reasons why this type of fish may be attracted to exploring the bottom of the tank and foraging for food. 

And, more importantly, if they are to breed, then you need to provide them with peat moss or soft sand for them to lay eggs in and bury them.

You can go for very fine gravel substrates if you want, but you should keep in mind that this will not create the same sense of belonging as being in the home and it will also reduce the chances of them doing any breeding.


Least killifish use foliage to hide from predators
Least killifish use foliage to hide from predators

As you know, killifish like to swim through vegetation in which they can hide from predators and hide. 

As a result of the light level in this aquarium, there is a significant problem with many aquarium plants. 

Killifish dislike bright light so there is a problem here too. Thus, you will have to choose plants that thrive in low-light conditions, which will require you to use potted plants.

Among the many choices, such as java moss, java ferns, or other fern types, or a cryptocoryne plant, make for good choices. 

A significant advantage of Java moss for breeding is that it is able to produce eggs that are suitable for laying eggs by killifish.

Having a few floating plants the size of a small window box is also a great way to provide some cover for your killifish.

Deco And Rocks

Besides rocks and hollow caves, a few driftwood pieces, driftwood blocks, and ceramics are also important in attracting killifish. 

It is the nature of these apes to explore and also enjoy some time alone on occasion.

It is recommended to add a small cave as well as a piece of driftwood that is hollow to a small killifish tank.

Tank Mates

It is important to note that if you intend to keep multiple male killifish together then make sure that they have plenty of space in their tank and that there are hiding spaces in which they can gain some private time from each other.

Apart from that, although its name may sound scary, a killifish, whether it’s called a yelp or a stingray, will usually get along well with most other peaceful aquarium fish. 

Among the best tank mates for Killifish, the Tetra is probably one of the best.

A Lid

In addition to the fact that killifish can jump like champs and they love jumping out of the tank, one other thing that you need to consider is that they are great jumpers. 

For your killifish tank, you must have a lid or hood to keep the fish dry and clean.

Video About Least Killifish 5 Gallon


What is the killifish density per gallon?

A killifish’s behavior will vary depending on its specific species. To illustrate this even further, every fish needs at the very least one gallon of water per inch in order to survive, and for this reason, it is unlikely that you will find any killifish that can live in one gallon.

How aggressive are killifish?

They do tend to be quite peaceful towards other male killifish and other fish which resemble killifish.

Killifish can sometimes become aggressive towards other male killifish as well as other male fish which resemble killifish.

Does it take a lot of effort to keep killifish?

There are also various types of killifish you can get, so it will depend on exactly what type you get.

Many plants can be easily cared for, while others can be very difficult to care for.

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