Choosing the first fish for an aquarium can be a daunting task. There are so many amazing fish to choose from, it can be hard to pick out just the right ones. All too often, a beginner fish hobbyist will pick out a fish that has specialized care requirements they are unable to provide, or they choose fish that get too large for their aquarium. Another issue that can arise is picking out fish that are unhealthy or are not socially compatible with other fish that they want. Hopefully, there is a friendly pet store employee to guide you into making the right choices for your aquarium, but if not, this guide is here to help you make those decisions.
For “desktop” aquariums, the choice of the first fish is the most critical mainly because these aquariums are small, and the first fish may be the only fish that goes into it. It is also the aquarium size range that can cause the most problems by adding too many fish or fish that get too large. Many aquarists start out in fishkeeping with tanks in this size range. Making a good choice at this point can ensure success in the future.
The fish for this tank should be small, generally between ½” and 2” at most. The bigger they are, the fewer you want to keep. Many hobbyists have visions of schools of fish swimming throughout the décor, but these size tanks do not lend themselves to schools of fish.
If you want to keep a diversity of species:
- Tetras are a good option for tanks of this size. It is best to narrow it down to a few species of tetra but avoid the more torpedo shaped tetras like neons and cardinals. When only a few neons or cardinals mixed in with other species are kept in the tank, they do not display their best. If your heart is set on a school of neons, go for a minimum of 12 fish and do not keep any other fish in the tank other than some Corydoras or a bristlenose pleco.
A better choice are tetras that have more diamond shaped bodies, like Serpae or Black Phantom tetras. A small group of 4-6 will look nice as individuals. Most likely you will have more than one male which will show off more impressive finnage and color as they display to each other.
- Another good group of fish are livebearers. Swordtails, guppies, platys, and mollies make up the variety of this group. It is best to avoid the swordtails and the sailfin mollies if your aquarium is under 10 gallons as they really need a larger tank with more space. Guppies, platies, and the common mollies will all do well in tanks under 10 gallons. To avoid conflicts, try to keep at least 3 of these fish together, preferably 1 male and 2-3 females. Males can be quite aggressive when it comes to breeding, so having multiple females avoids any one of them being the focus of attention and will reduce stress.
An important thing to remember is if you have male and female livebearers, you will eventually have fry – plan accordingly!
- There is another group of upper-midwater fish that do well in a small tank. These are the danios. Danios are small minnows that swim rapidly and almost constantly in the aquarium. The Zebra danio is one of the most common aquarium fish. There is also a genetically modified version available that glows. Keeping a small group of these fish will add a lot of activity to the aquarium. They tend to stay near the surface so they can be good to keep with tetras that tend to stay closer to the middle or bottom. Not all danios are suitable though; the Giant Danio should only be kept in larger aquariums.
- Lastly, there is a group of catfish called Corydoras that will do well in small numbers. A group of 4-6 Corydoras will help keep the substrate clean and add some unusual activity. There are many species of Corydoras, but only the smaller species should be kept in tanks from 5-10 gallons. The Panda cory, (Corydoras panda) and Salt and Pepper Cory (Corydoras paleatus) are good choices.
Like all bottom feeders, it is important to feed them directly and not just depend on them getting leftovers from feeding other fish. A sinking tablet like Aqueon Bottom Feeder Tablets or a small sinking pellet like Aqueon Pro Community will ensure that they get the correct amount of food.
Aquariums in this size range are bigger than a desktop but not quite into the arena of large aquariums. The range of possibilities opens a lot more at these size aquariums. You can still keep all of the small fish that do well in the smaller tanks (even more of them), but now you can start to keep some fish that get into the 3-4” size range. With these larger fish, sometimes their natural territoriality and aggression can be a concern, so care must still be made to not overcrowd them.
- The first group of fish for this size range are the Gouramis. The most common gourami are the various color morphs of the Three Spot Gourami (Trichopodus trichopterus). There are many different color morphs of this species including the Opaline, Violet, Gold, and Platinum variety. Another good species is the Pearl Gourami (Trichopodus leeri) which is one of the most beautiful of all gouramis.
With both species, you can tell the males by their elongated and pointed dorsal fins compared to the short and rounded dorsal fin of the female. It is generally a good idea to keep at least a pair of these fish, but you may want to add more females to reduce male aggression.
- The barbs are a large group of fish from the Cyprinid family and are found throughout Europe, Africa, and Asia. There are many different species of barbs that will do well in tanks of this size range. It is best to exercise caution and avoid any of the larger species such as the Tinfoil barb or the HiFin shark. These get quite large and require a much larger aquarium. Tiger Barbs, Black Ruby Barbs, Clown Barbs, Rosy Barbs, and Checkerboard barbs will do well in tanks of this size in groups of 6 or more. They are active swimmers that will generally stay in midwater and near the front of the glass.
- This is also an excellent tank size range for fancy Goldfish. Goldfish are one of the oldest, most popular aquarium fish and many different fancy strains to choose from.
A 29-gallon aquarium would be a good home for 3-4 of the fancy Ryukin or Oranda varieties. The more room they have, the longer and more luxuriant their fins will be. Feeding them a sinking diet like Aqueon Pro Goldfish will prevent them from ingesting air while feeding which can lead to buoyancy issues.
- While any of the Corydoras catfish mentioned earlier will also do well in a tank this size, another group of catfish generally termed “plecos” will also do well. The term “pleco” is generally applied to all species of the Loricariid family. Certain plecos are better for this size range than others. The “Common Pleco” or “Florida Pleco” will get too large for tanks of this size and should not be kept. A much better choice is the Bristlenose pleco (Ancistrus sp.) which maintains a small size and is a much better algae eater than the Common pleco. It is also available in many different color and fin strains.
Like all bottom feeders, it should be fed specifically and not just dependent on algae and scraps. Sinking wafers such as Aqueon Algae Rounds are important to ensure they get adequate nutrition. You can also feed them sliced cucumber to supplement their diet. The cucumber must be attached or weighted down so they can graze on it.
- Another fish that will enjoy grazing on sinking algae wafers and cucumber are the larger livebearers such as swordtails and sailfin mollies. These fish are algae grazers by nature and will also graze on cucumber like the plecos. When given more room to swim and move around, these fish will get up to their true size. Swordtails have larger females than males and they can get well over 3” long. Male sailfin mollies are typically larger, getting up to about 3” and display a very large sailfin to other males and females.
Some of you might be wondering why we haven’t talked about one of the largest groups of aquarium fish, the cichlids. Although there are dwarf species that would be great in tanks as small as 10 gallons, the cichlids generally dominate aquariums of this size range. Whether it is the graceful angelfish, the colorful mbuna, or the large and belligerent cichlids of Central America, most of them will do well in aquariums of this size.
- Cichlids can be broken down into two groups: the “New World” cichlids from Central and South America and the “Old World” cichlids from Africa.
New World cichlids from South America typically prefer softer and warmer water and include the popular angelfish which can be kept in small groups in tanks of this size range. Cichlids from Central America such as the Convict, Firemouth, and Texas cichlids can also be kept in groups but there will be more aggression when they pair off and breed. Providing a lot of rocks and décor for the cichlids to hide behind will help with aggression but it may be necessary to use a divider to divide them from each other.
The cichlids from the Old World can also be divided into 2 groups: the East African and the West African. For the West African cichlids, the most commonly available is the Kribensis (Pelvicachromis pulcher) which would do well as a pair in a smaller aquarium. You can keep several of them in a well-decorated, larger tank.
The East African cichlids can be subdivided by the two lakes they primarily come from. Lake Malawi fish are similar to each other in body shape. All of them are parental mouthbrooders which means that the female broods the eggs and fry in her mouth until they are ready to be released to fend for themselves. For tanks in this size range, you can keep groups or “harems” of these fish with one or two males and several females. You can also keep a diversity of species to create a diverse color pallet in the aquarium. It’s generally a good idea to crowd these fish to the capacity of the aquarium to reduce aggression. Keeping just a few will allow the dominant male to harass and target specific individuals, but in a crowded tank, that aggression is spread out. One of the most common and easy to keep of these cichlids is the Lemon Yellow Cichlid (Labidochromis coeruleus). This species is bright yellow and will generally have a black stripe running down the dorsal fin. It is one of the mbuna but also one of the least aggressive of these types of cichlids. They generally do very well in small groups and add a lot of color.
Cichlids from Lake Tanganyika are typically not as colorful, but they come in a wide range of body shapes and have very interesting behavior. One the easiest to care for and fun to watch of these is the Brichardi (Lamprologous brichardi). These fish exhibit excellent fry care, and the older siblings of the fry will actually care for them, too. A tank with a population of Brichardi can make for very interesting conversation. Other species to consider are the members of the Julidochromis genus or the shell dwellers in the Neolamprologous genus. Both types are interesting and easy to care for.
- If you are looking to keep larger fish, there are some bigger fish from Central America that might suit your appetite. The Firemouth Cichlid and Texas Cichlids will do well in tanks of this size. As cichlids go, they are of medium size but have big personalities. They can become instant pets in the eyes of their keepers and watching how they care for fry can be a fantastic experience.
Although the cichlids dominate in this size range with so many options available, there are other fish that will do great, too.
- Cyprinids are one of them. There are many species of barbs and danios that are too large for a small tank and need room to stretch out and swim. One of these is the Redtail shark (Epalzeorhynchos bicolor). This fish has been in the hobby for many years. It is critically endangered in the wild due to habitat loss but is aquacultured in the hundreds of thousands for the aquarium trade. They do best in larger tanks (bigger than 30 gallons preferably) and you should only keep one adult per tank. It is possible to keep juveniles together, but they will fight as they mature and will need to be separated.
Another cyprinid fish that is suitable for this size range is the Roseline shark (Sahyadria denisonii). This attractive species should be kept in groups of 4 or more individuals in a tank with a lot of open swimming space and some plants (real or artificial) for cover.
Lastly, is the giant danio (Devario aequipinnatus). They make good dither fish for cichlids as they are swift swimmers that will stay out of the cichlid’s way. Dither fish are fish that are added to make other fish feel calmer and more secure or to become targets for aggression that will prevent other, more vulnerable, fish be targeted instead.
- Another group of fish that are often used as dither fish are the Rainbows. Found in Australia and tropical islands in the South Pacific, the Rainbows are a midwater swimming fish that come in a wide assortment of colors.
One of the most popular of these is the Boeseman’s Rainbow (Melanotaenia boesemani). These are very colorful, easy to keep and can add a lot of color to the aquarium. Males will spar with each other by displaying their fins and deep colors as they shimmy against each other to display dominance. These displays are harmless, and the “loser” doesn’t get hurt. Rainbows are also generally good with small fish. They can be good additions to a tank with small tetras as a fish with a larger body size.
125 Gallons and Larger
It’s not typical to find a beginner starting out with an aquarium larger than 125 gallons but it does happen. Again, anything that can be kept in a smaller tank can also be kept in a bigger one. But now you can start to think about the really big fish. Some of these fish require specialized care and feeding but there are some that are easy enough for beginners.
- The Oscar (Astronotus ocellatus) is a popular fish for this size. Getting up to 14 inches long, they are big bruisers in the aquarium, but some can have the personality of a puppy. Available in a range of color patterns, they make for very interesting aquarium pets.
- Another good cichlid for this size tank is the Uaru (Uaru amphiacanthoides). Sometimes called the Poor Man’s Discus, the Uaru have a similar body shape and impressive size but lack the colors of the discus. They are, however, far easier to keep and do well on a diet rich in plant food like Aqueon Pro Herbivore pellet. But they are not safe in a planted tank as they will eat most plants, although they tend to ignore Water Sprite. Some people even use them to control invasive duckweed as they love to eat it.
- There are a variety of large catfish available at this size. The Florida Pleco will do well as an all-around scavenger. Giraffe catfish (Auchenoglanis occidentalis) is a large species (getting up to 24”) that is very peaceful and a suitable candidate for a big aquarium (at LEAST a 180-gallon). Another good choice and possibly the best choice is the Feather Catfish (Synodontis eupterus). This species doesn’t get as large (about 8”) and is very peaceful. What they lack in color is made up for with their long fin extensions and active social behavior. Several can be kept in the same aquarium. Often available as young juveniles, they can be kept in smaller tanks until they outgrow them.
We hope you enjoyed this article and found some tips for keeping fish in your aquarium. For more information, contact the experts at your local tropical fish store. Our website offers an array of resources, including the Ultimate Fishkeeping Guide to help you from start to finish and everything in between when it comes to fishkeeping. You can also find many of the species mentioned here in our care guides.