The following is a brief overview of some of the commonly encountered fish available in our local fish stores that grow to sizes difficult for the average aquarist to cope with in conventional aquaria. Hopefully this article will teach people what fish to avoid and they will further spread the knowledge on to others. Should you have a large enough tank and you're able to meet the needs of any of these fish then by all means go ahead and try them out. Though many of them are very inappropriate, some of them are commonly kept by those with the proper setups. Lima shovelnose, kissing gouramis, bichirs, plecos, the few brackish fish in this article, they all are good choices.
It is important to note that fish don't grow to the size of their tanks; they grow with the quality of the water. Many people will say they grow only as big as the tank allows and thus larger fish are alright in the smaller home aquarium. Not true, healthy fish will keep growing; in fact most fish never stop growing at all during their lifespan. It is water quality and improper care that stunts fish and as a result a stunted fish is an unhealthy fish. Done right, most fish have a similar growth potential in captivity as they do in the wild, this is why it's so important to pay attention to the size your fishes reach and to make sure you can accommodate them as adults.
This list is far from a complete write up. There are many other fish that could be placed on this list, and perhaps someday I will do another. Let this brief list serve as a warning that just because a fish can be found at the LFS does not mean it should be taken home or even sold for that matter. Readers are encouraged to do as much research as possible BEFORE they purchase any species no matter the size they reach or requirements they need.
Catfishes are an extremely diverse order of fishes known technically as Siluriforms. There are somewhere around 31 families of catfishes represented by thousands of species. Many of these fishes grow to extremely large sizes; indeed, some of the worlds largest freshwater fishes are catfish. It should come to no surprise then that many potentially large species are commonly sold in aquariums. Some of these do well in larger tanks; others should never be sold or bought at all.
These fish belong to the Ictalurid family (Bullhead Catfishes) unique to North America. Found wild all over the country in lakes and rivers these fish are very common in most fish stores. Typically it's the albinos that are sold but the normal ones are seen as well. Wal-mart, Petsmart and many other chain stores have them as a staple. These fish are very inappropriate for the average home aquaria. These fast growing fish are capabile of reaching over 4' in length. They are fast moving fish with large appetites and will quickly rid a tank of other fish. The good thing about them is that they are native to North America and as such can survive our climate. While they should never be released into the wild they can be placed in backyard ponds and treated much the same way as koi. For the indoor aquarium there are other species that would be better suited to take the place of a channel. Good alternatives are the smaller members of the Ameiurus genus, commonly known as bullheads. These fish reach a length of between 10-20” depending on the species. The white catfish, very similer to the channel only grow up 24” and like the channel has a forked tail.
These aren't actually sharks at all. These are catfish that hail from Southeast Asia and belong to the family Pangasiidae. Like the channel catfish these fish are also river dwellers capable of reaching 4' in length. Unlike the channel however these are social fish who prefer to live in shoals. They are also a very skittish and fast moving fish who startle easily. These three things combined (size, lifestyle and skittish nature) make for a fish that really isn't meant for even the largest home aquaria. It's not uncommon for these fish to swim full speed into the tank's glass and literally knock themselves out. In doing so they splash water everywhere, bang themselves up and often suffer from eye injuries (their eyes stick out from the sides of their head). It really is unfortunate that these fish are found in just about every LFS across the country. Because these fish come from a tropical climate only heated or indoor ponds are an option, unless you have these avoid this fish at all costs. Though I don't know anyone who keeps them, better alternatives to this fish would be Pangasius macronema, who only reach 11” in length, Pangasius micronemus who only reaches 4” and Pangasius nastutus who reaches 3”.
Though smaller then most of the fish in this article I feel it important to mention it based on how common it is in the hobby and how often it ends up in inadequate housing. Several species are sold on the market as “common plecostomus” most belonging to the hypostomus genus. These fish are one of the most abused in the hobby. Often they are purchased as cleaner fish. Though they are typically decent at eating algae they are often aggressive, messy (think oscar messy) and large growing fish who require a lot of food in their mostly vegetarian diet. They cannot subsist on algae and leftover foods alone, they require a unique diet of veggies and sinking catfish foods in order to thrive. They also reach 18 or so inches in length, making them only good options for the largest of tanks, no smaller then a 75g in my opinion. If you want a plecostomus for a smaller tank there are literally hundreds to choose from. Those most commonly sold include the bushynose, rubberlip and clown pleco. Often the bushynose and rubberlip prove to be better at algae cleaning then their larger relative. These smaller “plecos” only reach a mere 4-6”.
Kmuda Note: I got rid of an algae problem by getting rid of one of these giants. A 14” Pleco was generating so much waste, it was causing nitrates to go through the roof, creating a rather serious algae problem.
For sheer beauty and personality combined few catfish can match the awesome red tailed. These are large South American members of the Pimelodidae family. Their cute antics and colorful markings make these fish very attractive to people new to the hobby. Buyer beware however, these fish have huge appetites and at full size (over 40”) can eat a full grown oscar. Luckily, these fish are not as common as some of those mentioned previously but they do show up now and then and often end up in homes where they do not belong. Sadly, there are not smaller alternatives for this fish. Where personality is concerned the bullhead catfish again meet the requirements but they lack the color. Other smaller members of the family, such as the pictus catfish look nothing like their larger relative.
Like the red tailed both these fish come from South America and are members of the pimelodid family. Nether are overly common in most stores but luckily the smaller of the two (the lima) is seen more often then it's larger counterpart. TSN (tiger shovel nose) are able to reach close to 5' in length, the LSN is much smaller at only about 12-21” in length. In the right sized tank the lima can make for an impressive showfish, be warned though that like most other catfish they won't hesitate to eat smaller tankmates. These fish can also be difficult to convert on to dry food so frozen might be necessary. The markings of the tiger are very unique, and though the lima is a good alternative it's markings don't match those of the tiger. A smaller alternative for both are the many smaller members of the Pimelodus genus such as the four-line pimelodid and pictus catfish.
Found along the west coast of North and South America, size is not the biggest issue with this species. Though they grow large between 12-20” they certainly aren't impossible to keep for those with the right setup. They are misleading however. Often sold as freshwater fish these members of the Ariidae family (Sea catfishes) are actually brackish and saltwater. They spawn in freshwater habitats but as they mature they move to the sea and so the same is true in aquaria. As the fish age they will need more and more salt added to the aquarium. Unless you are able to handle a brackish or marine setup these fish are best avoided.
Cichlids are a very large and very successful family of fishes with members found in four different continents; Africa, Asia, North American and South America. There are between 1,300 and 1,900 different species. Some are as small as 2” while others reach over 3'. All species show some form of parental care for their eggs or young. There are many large species of cichlids, many that reach and go beyond the 12” range. I won't deal with those fishes because this is an oscar site, and members are familiar with what size tank a 12-16” fish needs.
There are 15 known and current species in the genus and all are large and all are ill suited for average home aquariums. They range in size from the 21” Cichla intermedia to the largest of them all; C. temensis who can grow over 3' in length. Though intermedia could make for a decent aquarium fish these are not sold in the United States at this time. None of the cichla species are very common in fish stores. They do show up once in awhile however and unless equipped with a very large aquarium or indoor/heated pond they should be avoided. There really are no alternatives for this fish, no cichlid can really match the color and unique body shape they possess. To even get close you would probably want to look at members of the black bass genus (Micropterus) in the sunfish (Centrarchidae) family. Though they lack the bold and colorful markings they occupy a similar nitch in the wild and share a similar body shape, probably why the peacock bass is called a bass in the first place. Most black basses also grow too large but there are a few smaller species that would work in larger setups. Redeye bass reach 18”, Guadalupe and shoal bass reach 15” and Suwannee bass reach 14”. Most of the black basses are difficult to come by and a lot of research might be needed in order to obtain one.
Like peacock bass these fish also aren't exactly common in the market but recently have started springing up in stores across the country, including the ones near me. They aren't giants but are still big fish capable of reaching 18-20” or so. The main reason I include it here is because of the incorrect information the tags at PetSmart have. They claim the fish reaches 8-12” and only needs a 20g tank. Obviously, if they reach 20”, a 20g won't work, it won't even work for a 12” fish. I notice many other tags give similar results, don't trust what the store claims. Always research your fish first. Given the right size aquarium these fish are impressive and care should be similar to that of other South American cichlids.
The family Cyprinidae (minnows and carps) is the largest family of freshwater fishes in the world, over 2000 species are known, they are mostly found in the Northern hemisphere being replaced by Characids (tetras) in the southern. The largest member of the family is the giant Siamese carp (Catlocarpio siamensis) who can reach 10” in length, luckily these are rare in the hobby. The smaller members of the family are well represented in the hobby, mostly with species that come from Asia and sadly not North America. Rasboras, barbs and danios are all members of the family, as are koi and goldfish. All of those listed below are native to Asia.
These fish are without a doubt some of the most commonly sold and commonly abused fish in the hobby, they may very well take the cake. Through genetic manipulation people have taken this fish and made a range of breeds that look nothing like their wild counterpart. Though many of these fancy breeds are alright for most aquariums, only reaching 4-7” there are some that, like their wild cousins, are very large growing fish only suited for pond environments. Common and comet goldfish are very much like their wild relatives found naturally in Asia. There are minor differences such as color and finnage but where size is concerned you may be surprised at just how large they can grow. These common and comet goldfish are typically sold as feeder fish, or won at state fairs. Fair goers be warned, it is not uncommon for these fish to reach 12-23” in length. Many fish sites (and sadly, many goldfish forums devoted to the species) will tell you that the minimum tank size for a common/comet is 20g. Don't be fooled, there is no way a 12-23” fish can live in such a tank and no matter how common or cheap they are they still deserve conditions to meet their needs. These fish are best placed in ponds, should you want a goldfish but cannot afford the tank or pond needed for the giants simply get a smaller breed.
Close relatives of goldfish, koi are very popular with pond owners, and aren't found all that often in actual aquariums. Koi are actually selectively bred common carp and though the colors are different they are very much the same fish and capable of reaching the same size, over 4' long. These are very large and long lived (30+ years) fish so much consideration must be given if you are to acquire them. Setting them free in wild places is NOT an option, sadly both carp and goldfish are responsible for a number of problems in North America where they destroy plants and compete with native species. If you would like to own a koi but cannot afford a large pond setup then simply scale down and go with common goldfish. If you want something even smaller go after the smaller fancy goldfish strains.
Tiger barbs, cherry barbs, Odessa barbs; there are a lot of “barbs” in the hobby and while those listed above stay relatively small the tinfoil certainly does not. These are large (14”), fast, shoaling species. Their fast moving, shoaling nature makes them ill suited for even most larger home aquariums. Given the right sized tanks they make for fine large community or dither fish. Good alternative dither/target/large shoaling species include the silver dollar and golden shiner. Good alternative cyprinids would be any of those listed above and again the golden shiner.
Here again is another popular, large cyprinid that's often abused by those uneducated to the hobby. Bala sharks are a staple in most fish stores and are commonly placed in smaller community tanks. Bala sharks can reach between 12-16” and like the tinfoil (and so many other cyprinids) they are skittish and do best in shoals. They are the sole member of their genus.
These fish are in very many ways similar to carp and larger goldfish, both in behavior and appearance. And like carp and goldfish they also grow very large, over 22” in length. They are an aggressive species towards their own kind. Luckily for their admirers they have close relatives in the hobby who stay much smaller. The red-tailed black shark (Epalzeorhynchos bicolor) is nearly identical, save for its red tail. These fish only grow to about 6' long but like their large relatives are aggressive towards their own species. There is also the rainbow shark (Epalzeorhynchos frenatus). They grow to about the same size as the red-tailed and their care requirements are much the same.
In Giants Among Us: Part 2 I cover Anabantoids, Characins, Knifefishes and more.
A note on photographs: Originally I set out to locate photos for each fish but was unable to get permission from their owners. The photographs that I was able to get were all kindly provided by Jean-Francois Helias, owner of Fishing Adventures Thailand. (http://www.anglingthailand.com)