Choosing and Introducing Fish to your Aquarium

Selecting and introducing fish into the tank is one of the most enjoyable parts of tropical fishkeeping. There are many hundreds of different species to choose from, each with their own individual characteristics and habits.

However, selecting the right species for your aquarium, and introducing them correctly, can make all the difference when it comes to achieving a balanced environment. Stick to the rules and you will be able to have a diverse and interesting selection of fish, whilst avoiding any potential problems.

Selecting Fish
When choosing which fish to keep in your tank, there are a number of things to bear in mind:
Knowledge: Certain fish are not ideal for beginners, e.g. Discus and Rift-Valley Cichlids. If you are new to the hobby, then the best option is to go for a "community" aquarium.

• Swimming levels: Different fish prefer to inhabit different areas of the tank. For example, some fish prefer to swim just under the water’s surface, whilst others prefer to swim in the middle of the tank or scuttle around on the gravel and rocks.

• Social needs: Many fish need to be kept in shoals, to make them feel secure and happy. Such species will need to be bought in groups, otherwise they will usually hide away and may become unwell. On the other hand, some species prefer to be on their own, or do not mind being kept singly.Therefore, finding out about a fish’s social requirements before buying it, is very important.

• Compatibility: Some fish have a tendency to be either aggressive, or particularly sensitive, and are therefore best left out of most aquariums.You should aim to only keep species that will cohabit peacefully. Such species are referred to as “community” fish.

• Feeding: A good quality flake food, such as TetraMin, orTetraPro Crisps, will offer your fish a complete diet, but it is important to be aware of all your fishes’ specific feeding needs. Some fish, for example, may prefer to feed off the bottom of the tank, or in the middle of the water rather than from the surface. In addition, certain species may need a particular food, for instance a vegetarian crisp, such as TetraPro Vegetable. Meeting the specific needs of your fish is important, but easy thanks to Tetra’s range of complete foods (see the ‘Feeding Your Tropical Fish’ leaflet for more information).

• Water Conditions: The majority of community fish that are commonly seen for sale are fairly well adapted to the water conditions found in most home aquariums. However, to make certain that conditions in your aquarium are suitable, it is worth talking to your aquatics outlet about checking them before starting to introduce fish.

Before purchasing a fish, it is important to discuss your selection with your aquatics outlet, as they will advise you about its needs and suitability.A good tip is to keep a record handy of what species you have in your tank, so that the person advising you can ensure that they are compatible with your new purchase.

Types of Fish
There a many hundreds of fish available through the aquatics trade, and it would be impossible to mention them all here. The following is a brief description of some of the most common groups, although you should always find out the requirements of individual species before buying them.

• Tetras: A large group of fish, containing a huge range of species.Although some varieties of tetra originate in Africa, the majority of those that are seen for sale are South American.They are popular aquarium fish and most are suitable for community tanks, as they tend to be small and non-aggressive.The most popular types include the neon tetra, cardinal tetra, black widow tetra, lemon tetra, red-eye tetra, serpae tetra, and so on.They are shoaling species and need to be kept in groups.

• Barbs: Another large group of fish, with the majority of aquarium species coming from Asia.Although the majority of those seen for sale are small, peaceful species, there are a few that can grow large and be quite boisterous.Therefore, it is important to ask about a species before purchase.The majority of barbs prefer to be in shoals, with popular varieties including the ruby barb, rosy barb, pentazona barb, golden barb and checker barb.

• Rainbowfish: In recent years, rainbowfish have become more popular for community aquariums.This is due to their relative ease of maintenance and their impressive colours. Rainbowfish originate from Asia and Australia, and prefer to be kept in a shoal.Although there are one or two small species, most grow to a reasonable size and therefore need plenty of room. Popular species include the red rainbow, praecox rainbow and boesemani rainbow.

• Catfish: There are many different varieties of catfish, coming from all over the world. Many of them are predatory or aggressive, and therefore unsuitable for a community tank, and so it is important to choose carefully and seek advice. Many species of catfish prefer to remain on the substrate, and may only come out at night to begin with. However, with the correct care and feeding, they will soon be tempted out. In addition, some shoal whilst others remain solitary, so doing some background research is important. Popular community species include Corydoras species, bristlenose plecostomus (“sucker-mouth” catfish), glass catfish, flagtail catfish, and whiptail catfish.

• Livebearers: These fish are notable for their ability to give birth to live young, rather than laying eggs like most other fish.When kept in home aquaria, it is not unusual for livebearers to reproduce quite prolifically.The majority of commonly available livebearers prefer to be kept in groups, and there are many different colour varieties of most species. The most commonly kept livebearers are guppies, mollies, platies and swordtails, all of which are suitable for community aquaria.

• Gouramies: Slightly larger than most other community fish, gouramies make good additions to the community aquarium.They usually prefer to be kept in small groups, and are on the whole peaceful.They are characterised by their ability to breath atmospheric air, through the use of a specially modified organ in the top of their gill chamber. Popular varieties include the opaline gourami, gold gourami, pearl gourami and dwarf gourami.

• Loach: Loach are another large group of fish, most species of which prefer to spend their lives on the bottom of the tank, searching through the substrate for food. Most are very active, but some can be quite secretive and may hide away until feeding time.They vary in their temperament and so you should ask about any species that you are interested in. Commonly kept varieties include the clown loach, horse-faced loach, kuhli loach, and orange-finned loach.

For more information on the care of the above fish, please ask your aquatics outlet or contact us here at the Tetra Information Centre.

Introducing New Fish
If your aquarium is new, before adding fish you should refer to the ‘Setting Up a Tropical Fishtank’ leaflet.After purchasing a new fish, your aquatics dealer will package them ready for you to take home. Fish can survive for long periods of time in properly packaged transport bags, but it is very important that you get them home as quickly as possible.This is because transportation is a stressful process, and the longer the fish has to endure it, the more likely it is to weaken them. Ideally, you should have a polystyrene box into which you can put the bag to insulate it, and a lid to cover it with.At the very least, the bag should be kept in the dark and away from loud noises or vibrations.

Once you arrive home, you should float the bag in the aquarium for twenty minutes, to allow it to equalise with the temperature of the water.The next step is to open the bag and roll down the sides, so that it is still floating on the surface.Over the next thirty minutes or so, you should gradually replace the water in the bag with some from the aquarium.This allows the fish to get used to their new water conditions slowly, and avoids unnecessary shock.

It is a good idea to turn the aquarium lights off during this acclimatisation, and leave them off for the rest of the day. This helps to reduce any stress that the new fish might be experiencing.

Aftercare
Newly introduced fish are more vulnerable than those that have been in the aquarium for a long time.This is because they experience a certain amount of stress after transportation, and while they are settling into their new environment.This makes them more susceptible to any decreases in water quality or disease-causing microbes.

In the days after adding fish to the tank, it is a good idea to test the water regularly with Tetratest ammonia and nitrite kits, to ensure that water quality is being maintained. Slight rises in ammonia or nitrite may occur because the filter has to increase its bacterial population to cope with the new fish load. Small partial water changes using a water conditioner such as Tetra AquaSafe will keep levels in check, until the filter has caught up.

Follow this guide and your retailer’s advice, and adding fish to your tank will be a trouble-free and enjoyable experience. For more information about stocking a new aquarium, see the ‘Setting Up your Tropical Fishtank’ leaflet.