What fish can I keep together in my Aquarium?

Having an aquarium in the home or workplace is a relaxing asset, however it is vital that you understand which fish will live well together to ensure the aquarium thrives. This can be an overwhelming decision when faced with the thousands of cold-water/tropical fish breeds to choose from. 

As a novice, it can be easy to select fish which you like the appearance of, however this is often a mistake. There are many aquarium fish which will happily live together, but equally there are many that will not tolerate one another. Here is our guide to selecting fish in your aquarium.

Why is it important for aquarium fish to get along? 

This may seem self-explanatory, however it is important you understand the basics. As the aquarium owner, you have the power and responsibility to ensure the fish tank is functioning correctly from an equipment perspective (i.e. filter/filtration, heater/temperature etc.), but also from a fish interaction perspective. To put it bluntly, aquarium fish that don’t get along can become bullies in extreme circumstances, which will add a great deal of stress to the aquarium environment. While this is generally species specific, you can on occasion be stuck with a boisterous fish which will bully members of the same species. 

Why are my fish fighting in my aquarium?

As with any animal, there is always the potential for conflict, which tends to result in a fight. The fish world is no different. There are several reasons why a fish may seek this outcome:

• Resources – Fish can become obsessive with a number of things in the aquarium such as territory, food, plants and hiding places such as rocks. They will often chase off rivals when they see them as a potential competitor for the resource

• Mates – Depending on the species of fish, you need to keep an eye on your sex ratios (i.e. male – female). Certain species such as Betta fish will often fight to win control of a female and the outcome is often injury or death.

• Personalities – Certain fish species are shy while others are incredibly aggressive by nature. For this reason, it is important to research a species or speak to an expert prior to adding these to your aquarium.

What are ‘fin nippers’?

Fin nippers can be any fish that are typically aggressive and/or territorial and will actively seek out fish with long flowing fins and bite them. Fin damage can be fatal to fish, so it is important that you must not include fin nippers in a peaceful aquarium containing fish with fancy tails such as Goldfish, Guppies or Angelfish. 

The most common fin nippers tend to be barbs and cichlids, however this can vary from individual species, i.e. Golden Barbs and Key-hole Cichlids are fairly peaceful. Likewise, placid fish such as Platys can on occasion be overly aggressive and turn into a fin nipper, making them a problem. 

If you find yourself stuck with a problematic fin nipper in an aquarium, the best solution is often to re-home the offending fish. To avoid purchasing a problematic fish, it is best to do your research prior to buying. 

How to select the right fish for your aquarium

To begin with, the easiest way of selecting fish is to choose fish which are not aggressive or territorial and have similar environmental requirements. This rules out most predatory fish. In a cold-water aquarium, there is generally less selection, and so this tends to be goldfish and fancy fantails, none of which are notably aggressive.

In a tropical aquarium there is a much wider selection, and we generally refer to the peaceful fish as community fish. An overview of community fish which fall into this category are as follows:

• Small Catfish i.e. Plecostomus
• Corydoras
• Danios
• Small Gouramis
• Guppies
• Mollys
• Swordtails
• Platies
• Loaches
• Harlequin Rasboras
• Tetras
• Male Bettas (although we would advise restricting these to one per aquarium)
• Rainbow fish
• Minnows

Certain species of more aggressive tropical fish are okay to keep in groups but as a rule of thumb they should be kept with groups of the same, or similar species, which are detailed below:

• Barbs (i.e. Tiger Barbs, Cherry Barbs, Burmese Odessa Barbs)
• Cichlids
• Predators such as Piranha 

Can aquarium fish eat each other?

Yes, omnivorous fish (i.e. a fish which eats both meat and vegetation) which grow to a notable size will often consume other fish if they will fit in their mouth. A typical example of this is keeping black ghost knife fish with neon tetras. A young knife fish will often start out life in the aquarium as a great fit for a community tank, however the moment it can fit small fish in its mouth, it becomes a threat.

Which freshwater fish are considered to be community fish?

At the most basic end of the spectrum, live bearers and tetras are considered to be community fish, although there are other species which can be included in a traditional community tank. See our list below:

• Tetras (e.g. neon tetras, cardinal tetras, black phantom tetra, Ember tetra, Congo tetra, etc.) - This group of fish are easy to care for and are a staple of beginner aquariums. They’re small in nature, come in bright striking colours and prefer shoaling in numbers. 

• Guppies – Guppies come in many colours and are known for their brilliantly beautiful tails. Guppies are live bearers and prefer being in groups of 3 or more. They’re very easy to breed providing there is a combination of males and females in the aquarium. 

• Mollies – These are small peaceful fish which are available in a variety of shapes, colours and patterns. Like guppies, they are simple to breed, providing there are both males and females in the aquarium. If you’re not looking to breed them then be sure to only purchase a single sex.

• Danios (e.g. Zebra Danio, Pearl Danio, Golden Zebra Danio etc.) – Danios are small, surface dwelling fish. They’re incredibly active and fascinating to watch as well as being extremely hardy, making them ideal for community aquariums. They can tolerate both tropical and cold-water aquariums.

• Platies – Platies are another colourful live-bearer. Normally they are Orange/Red, but other colours are available. This is another small, easy to breed livebearer species, and they are perfect for community aquariums. They get on very well with other livebearers.

• Swordtails – The swordtail looks similar to a Platy but with a longer bulkier body and in the males, there is a sword-like extension to the tailfin. Again, there are many colour variations of the species. The Swordtail is another easy to breed livebearer. 

• Gouramis (e.g. Honey Gouramis, Pearl Gouramis, Neon Dwarf Gouramis, Blue Gouramis etc.) – Gouramis exist in both standard and dwarf varieties. By nature, they are peaceful and are available in some very striking colours.  

• Killifish – There are over 700 species of Killifish, and they come in just about every colour. They are very hardy and ideal for community aquariums. If possible it is best to have 1 male per aquarium as the males can be aggressive to each other.

• Bettas / Siamese Fighting Fish – Bettas are extremely colourful tropical fish with long flowing fins. While the name ‘fighting fish’ sounds threatening, they’re only a problem when there is another male present in the aquarium. Kept singularly OR with a harem of females, they make a great fit and add a splash of colour in a community aquarium. 

• Plecostomus – Plecostomus are armour plated catfish with sucker shaped mouths. You will often see them hanging off the glass of an aquarium, eating algae in the process. They’re long living fish and some species can grow large, so ensure your aquarium size is adequate before introducing a species. 

• Rainbowfish – Rainbowfish originate from Australia and Southeast Asia. They’re brightly coloured, peaceful shoaling fish which will often occupy the upper water level of an aquarium. 

• Corydoras – This bottom dweller is another species of Catfish which will spend its time finding leftover food amongst the substrate. They’re very calm and will live peacefully together. They prefer to be in groups of two or more. 

• Angelfish – Angelfish can grow fairly large (i.e. 6” long) and are a great fit for a peaceful community aquarium. The aquarium should be suitably sized to allow for their growth. When Angelfish become mature and find a partner there are instances when males can become aggressive and territorial to other fish in the aquarium, but this is rare. 

• Goldfish – Goldfish can be kept in tropical aquariums, but typically exist in cold water systems. They are very peaceful and come in an abundance of shapes and colours. Goldfish can be quite messy, so it is important to ensure you have suitable filtration. 

Which cichlids are considered to be community fish?

Cichlids are some of the most beautifully coloured tropical fish available, but many Cichlids can be aggressive. Several species of Cichlid however can be kept in a traditional community aquarium which we will detail below:

 

• Apistogramma – These south American Cichlids are a great fit for community aquariums, providing they are kept as singles. Other Apistogramma in the aquarium can cause unnecessary aggression. While they’re generally peaceful, they are in fact predators and will eat any small fish they can fit in their mouths.  

• Angelfish – As previously mentioned, Angelfish are a great fit for a community aquarium, and they are also a variety of Cichlid. 

• Blue Acara – Blue Acaras are very hardy and can also be very colourful. On top of this, they are very peaceful and can be kept in numbers, making them a super fit for a community aquarium. Blue Acaras prefer warmer water and sandy substrate though they will live comfortably in most tropical aquarium conditions. 

• Rams (German Blue Ram, Bolivian Ram, Golden Ram etc.) – Much like the Blue Acara this is a striking, colourful peaceful Cichlid which will live comfortably in most community aquariums. 

• Keyhole Cichlid – The Keyhole Cichlid is a very shy aquarium fish which likes to hide in caves. Their timid nature makes for a very placid fish which will slot into a community aquarium. 

• Rainbow Cichlid – Rainbow Cichlids are very easy to keep and breed well in captive aquariums, making them ideal for beginners. They have a peaceful nature making them a great fit in a community aquarium.

While the fish listed above are great fits for a traditional community aquarium, other species of Cichlid may be put together in a Cichlid community aquarium. An example of this is a Malawi OR Tanganyika aquarium, where many species (which would normally live together in the wild) are kept in a single aquarium, without any issues. The set-ups of such aquariums are different to a standard aquarium setup, so it is best to research prior to adding fish. 

Can shrimp be kept in a community aquarium?

Shrimp come in a variety of sizes – some such as the bamboo shrimp can be 3-4” in length. On the contrary, some species, such as Cherry Shrimp, are extremely small and delicate. Fish by nature are opportunistic and if a shrimp will fit in a fishes mouth, you can bet it will try to eat it. So, the answer to this boils down to the size/temperament of both the fish and shrimp in the aquarium. 

It is much easier to keep a Shrimp only aquarium, however if you’re set on having both Shrimp and Fish ensure you get suitably sized species of each, i.e. Guppies and Shrimp will often peacefully coexist. Fish often investigate moving objects such as shrimp with their mouths, and the act of mouthing a small shrimp will often be fatal for smaller species. 

What types of community fish eat shrimp?

We would expect the following community species to eat Shrimp (subject to size):

• Goldfish 
• Gourami – Both standard sized and dwarf
• Bettas
• Angelfish

While there are exceptions to the rule, it is best to steer away from larger fish when keeping Shrimp. Shrimp are commonly a part of a fish’s diet in the wild, so many fish will see small shrimp as a tasty snack.

What types of community fish eat snails?

Snails can be an asset or a pest in a community aquarium. If you are overrun with Snails it is often best to let fish solve the problem for you, rather than turning to chemical treatments. The best snail eaters are without doubt the Loaches – notably Clown Loach, Yoyo Loach and Pakistani loach. These bottom dwelling fish will seek out small snails and consume them as a natural food source, which can be highly effective in treating snails. Other fish species which like to consume small snails are Gouramis and Bettas. 

Can Koi Carp be kept in an aquarium?

Koi Carp are large cold-water pond fish descended from wild carp. While they can live in aquariums it is often not an ideal fit, particularly if the aquarium is small. Koi Carp can grow very quickly and will often outgrow small ponds, so aquariums must be suitably sized. The simplest way of having Koi Carp is to start small – ideally 4” or less. As a rule of thumb your aquarium should have 1 cubic foot of space per inch of Koi. If you have a large aquarium then yes, Koi Carp will be OK in there until they outgrow the space, at which point they will have to be rehomed.

The second consideration of keeping Koi Carp in an aquarium is adequate filtration. Much like goldfish, Koi Carp eat a lot and are thus incredibly messy. An internal filter may be sufficient, however an external filter would be better. 

Aquariums can be an ideal place to raise juvenile Koi Carp. An aquarium provides a safe space which can be micromanaged to ensure the conditions are optimum. In these circumstances, smaller aquariums with lower levels of filtration will be acceptable. 

What fish can live with Koi Carp in a tank?

When keeping Koi Carp in an aquarium we recommend keeping it as a Koi Carp ONLY tank. If there is an outstanding desire to introduce other species, then we would suggest introducing other similar cold-water species. The aquarium will most likely be kept at room temperature so the species must be able to tolerate this. Typical examples of aquarium fish which would be suitable with Koi Carp are as follows:

 

• Goldfish
• Orfe
• Plecostomus
• Tench
• Weather Loach

 

Please note, most of the species above also grow to a considerable size so you really should have a suitably large aquarium to house the fish. 

In conclusion...

To conclude, it is incredibly important to research fish extensively before adding them to your aquarium. If you’re at all unsure about anything, or have any further questions, feel free to contact our team of in-house experts at Complete Koi & Aquatics