Giants Among Us: Part 2

Posted in About Fish

By Sandtiger

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'ure 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.


Anabantoids are native to Africa and Asia and many are well known for their ability to breathe air with the aid of their labyrinth organ. These fishes are common in the hobby, represented by many popular fish such as the Siamese fighting fish and the dwarf gourami. They are staples in every LFS and popular among aquarists of varying levels of experience. Though many are kept in community aquariums there are a couple that are better left out of the average aquarium.

Giant Gourami (Osphronemus goramy)

Though not particularly common in the hobby I feel it important to mention these fish. When young it is easy to mistake this fish with other gouramis and assume that they would make a good choice for the community tank like so many of their small colorful relatives. But these fish are capable of getting quite large, up to 28”. Among large fish keepers these are a popular species, despite their some what ugly appearance when fully grown. It is said that their personality is comparable to that of an oscar, some say they even overshadow oscars in that department. It is important to remember their size though and stick with their much smaller relatives if you are unable to house them properly.

Giant Gourami

Kissing Gourami (Helostoma temminckii)

Alright, so these fish aren't the largest in this article but they still do grow large and are included because so many people mistakenly buy them not knowing their true potential. They are said to reach 12” in length, though personally I have never seen one beyond 8-10” but even at that size they are impressive by gourami standards. They make fine additions to larger community's but can be aggressive at times so tankmates bust be chosen carefully. They also prefer a veggie rich diet, something not true for most gouramis.

Kmuda's Kissing Fish: These fish are a long term commitment, this one is over 20 Years Old and they don't stay cute little smoochers for long


This is a diverse order of fishes with over a thousand species divided in 15 families mostly found in the Southern half of the globe in places like South America and Africa where cyprinids are not as common or completely absent. Many of these are well represented in the hobby. Species like the neon, rummynose and blackskirt tetras and silver dollars. Many other fish are also in this order however, fish like the piranhas, African tigerfish and freshwater hatchetfish. Most commonly sold are small to medium size, others grow very large. One very large tetra in particular is all too common in fish stores and in the tanks of ill equipped (or ill informed) fishkeepers.

Red Belly Pacu (Piaractus brachypomus)

Often bought because of their similarity to red belly piranha it is actually the piranha who would make the better aquarium subject. These are true giants of the characin world. Sadly, like so many other fish these are very common in stores, often sold alongside oscars. Many people come to this site asking about these fish only to find that they should not have bought it in the first place. These guys can reach over 34” in length and are known to be very fast growers. They are true tankbusters capable of incredibly powerful bursts of speed and even if you did have a tank large enough for one, they aren't comfortable unless they are in shoals. This makes them an almost impossible fish to keep for most people. I have heard so many horror stories about these fish. Often they are caught my anglers due to people who release them into the wild¦unable to handle their requirements. Often times people are forced to kill the fish, mostly do to the fact that no one wants a large sized pacu; not even most public aquariums. Avoid this fish at all costs. A good alternative to these fish would be silver dollars. Their behavior and appearance is very similar. There are several silver dollar species, most only reaching about 6” or so.

Pacu, the definition of a tank buster

Black Pacu (Colossoma macropomum)

If you were horrified at how large the commonly sold red-belly gets just wait till you hear about this fish. At 42” or more these fish cut past the 34” mark. Though not as commonly sold as the red belly they do appear in the market and like the red belly the same rules apply here. Avoid these fish and get a nice shoal of silver dollars instead.


Arowanas are a primitive group of fish that belong to the family Osteoglossidae. Unlike with the other species I mention I won't break this one down by species. They all grow large. Luckily they are expensive fishes so new comers don't typically buy them and those that do are familiar with the species. Even still, I think it is still important to mention them here. There are 10 species of arowanas divided into two subfamilys. They are found in South America, Asia, Africa and Australia. The silver arowana is the one most typically encountered on the market, it's also the cheapest but still capable of growing 3-4' long. The Arapaima gigas, though rare in the hobby is one of the worlds largest freshwater fish. These are very powerful animals; quick surface feeders and excellent jumpers, capable of leaping 6' into the air. There really is no fish comparable to the arowana, about the only one I can think of is the African butterfly fish. At 6” they are much smaller alternatives but look almost nothing like arowanas except for perhaps their faces. They are similar in regards to behavior and feeding habits. They also belong to the same order as arowanas.

Arapaima gigas


Knifefish are a unique group of fishes that are alike in many ways but not all related. Some belong to the same order as the arowana, others like the Gymnotiformes make up an order all their own with families within that order.

Clown and Royal Knifefish (Chitala ornata and blanci)

These are fairly common fish in the hobby despite the ability to reach 31-36” in length. Many fish stores get them in from time-to-time and it seems Petsmart (at least the one near me) always has clowns on hand. They come from Southeast Asia and are actually popular food fish over there. Good alternatives for these guys would be smaller knifefishes, related or not. These are the knifefishes within the Osteoglossidae order.

Clown Knifefish

Black Ghost Knifefish (Apteronotus albifrons)

These fish and their relatives are interesting in that they emit an electrical current in order to navigate their native waters (often very dark and murky). There are many smaller members of the family but probably the most common in local fish stores also happens to be the largest in South America, black ghost knifes can reach 20” in length. Not an impossible fish to keep by any means but larger facilities are defiantly required for them.


This is a very interesting family of fishes that are mostly found in salt and brackish waters. All members of the family have an adhesive disk formed by fused pelvic fins and can stick to tank walls and other surfaces. This is one of the largest families of fish with over 2000 species. Some of them are among the smallest fish in the world at a mere 3/8th of an inch. Most species are small; some can reach a foot or more. Mudskippers are members of the goby family.

Violet Goby (Gobioides broussoneti)

These are very strange looking fish, unlike any other you're likely to find. Often sold in stores they are typically overlooked because of their ugly appearance. Still, others like how they look and buy them, usually not aware of the requirements they need. Like the previously mentioned Columbian shark these are brackish water fish, found natively on the coasts of North and South America. They are also large fish, growing up to 22” in length.

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 kindly provided by Jean-Francois Helias, owner of Fishing Adventures Thailand. ( The picture of the kissing gourami was provided by Kmuda.