There are many different types of aquaria. Coldwater, tropical, fresh, salt, community, aggressive, fish only, planted, reef…..the list goes on and on. This is by no means an exhaustive list. The first major category split is the division into temperature -cold water, and tropical.

Coldwater, for the most part, refers to goldfish aquaria, though there are other fish kept by hobbyists that may also be suited to this type of setup.(many hobbyists keep local temperate/cold water aquaria that they stock with locally available species), such as certain barbs and minnows, dace, etc. . There are many varieties of goldfish available today, from the common ‘comet’ to the more ‘outlandish’ varieties like the lion head oranda. Goldfish aquaria do not require a heater, being cold water fish, but they do require more attention to water quality, as they are more sensitive to ammonia and carbon dioxide issues of water chemistry. They do require a lower stocking rate in fishes per gallon for comfort and longevity, and are not conducive to maintaining a planted aquarium. Due to their greater overall sensitivity to waste issues and oxygen levels, the minimal size aquaria for one goldfish should be 10 gallons. Bowls are a huge ‘no-no’ for goldfish!! Fluidized bed, and biowheel filters are highly recommended, due to their ability to rapidly process ammonia (the first major waste product that fish (and hobbyists) need to deal with).The ‘fancy’ varieties with enlarged eye sacs (bubble eye, celestial, telescope) require an aquarium decorated without any sharp objects, and sponges on all filter strainer openings, to avoid puncturing the delicate external membranes.

Tropical denotes the ‘rest’ of the fish world we deal with as hobbyists, and it has many ‘sub-categories’, from 8 ounce betta bowls, small size fish ‘community’ aquariums, to the ‘behemoth’ (usually cichlids, but there are plenty of non cichlid fish, as well, that reach very large sizes) tanks.

Tropical community aquaria

The most prevalent beginner’s type of aquarium  is  the tropical ‘community’ aquarium, which may be designed completely with ‘artificial’ décor (plastic plants and ornaments), a mix of both artificial and real decorations, or exclusively ‘au naturel’- utilizing real wood, rocks, and plants. Community tanks split further into ‘peaceful’ and ‘aggressive’, and there can also be a further split into large size and small size fish groupings. The most common freshwater aquarium most folks start keeping is the ‘classic’ community tank-whether planted or not-the inhabitants are usually the small, more peaceful egg layers and livebearers that reach a size of 1-2 inches. Tropical, of course, denotes a warm water environment, usually with a maintained constant temperature of 78° F, or thereabouts, which is accomplished by using a submersible thermostatically operated heater. It is highly inadvisable to mix goldfish with tropical fish, due to the differing environmental requirements of the above mentioned groups. Filtration is easily accomplished by any of the wide variety of power filters-from the hang on the back types (power, fluidized bed) to external canisters. Most novices are familiar with at least a few of the species before they even begin, if not by name, then by what the fish looks like. (How many haven’t heard of a guppy?).Tropical aquaria are usually kept at some sort of ‘compromise’ chemistry-egg layers and livebearers have slightly different preferences for water chemistry, so the community aquaria are kept at the middle of the road point, that both groups can deal with comfortably.

Planted Community Aquaria

Another type of tropical freshwater setup is one where the plant ‘population’ is as greatly, or more, emphasized than the animal population. The care of a planted tank is more involved, and can be just as challenging and rewarding as a saltwater reef tank. Planted aquaria provide for ‘built in’ benefits in the form of natural waste uptake, increased pH stability, etc. One does, however, need to take into account the needs of the plants (lighting, fertilizers, etc) as well as the needs of the fish. A well designed planted tank can be quite stunning, visually. Just like their saltwater reef counterparts, planted aquaria do tend to lead to healthier fish-not just because of the better water conditions, but because of the increase in natural cover provided by the plants themselves. A regular trimming will be necessary occasionally, as the plants grow, and more attention to water chemistry is required, via test kits. The planted aquaria ‘movement’ has greatly developed over the past few decades, and there are plenty of books and websites/discussion forums available online.

Planted aquaria can be the most challenging freshwater systems to properly maintain, and are considered on a par with reef tanks, both with regard to the visual appearance, and the greater  ‘involvement’ required with respect to following and maintaining the proper water chemistry. However, there’s a wealth of information, both in print, and online, to ensure that anyone can succeed relatively easily, with just some extra attention to husbandry detail. Smaller planted aquaria can be quite attractive, and, even with the ‘extra effort’ required regarding meeting the plants’ requirements, larger systems can be maintained with the same half hour or so of work weekly. Another advantage (depending on how one looks at things) is that a mono-species tank can be very impressive, due to the added visual ‘oomph’ the plants provide. A nice size tank, covered with lush green growth, can be a ‘knockout’ with nothing other than a school of 50 cardinal tetras glowing and darting about among the ‘scenery’.

Cichlid Aquaria

The cichlids represent the largest, most diverse group of fishes kept in the freshwater aquarium hobby, and they range in size from ‘dwarfs’ (which aren’t really dwarf, but in the context of the cichlid world, where many, if not most, fish reach 6 inches plus, it’s understandable that  a fish that reaches a maximum size of 2-3 inches  would be called a ‘dwarf’).The term ‘cichlid’ refers to the way these fishes are built/structured, and in no way relates to the size or temperament of the fish itself-this is why one needs to deal with the various ‘groups’ of cichlids specifically.

Cichlids also represent the widest habitat diversity, as well, in the freshwater world, occupying the entire ‘safe’ water chemistry spectrum of habitat the world over, from the soft acidic waters of the Amazon river basin, to the hard alkaline waters of the great lakes of Africa. Their size, range and temperament are just as varied, as well, from bullying jerks only 3 inches long, to foot long and longer ‘apathetic’ types that would rather just gaze at another fish than even begin to ‘mess’ with it. Some will coexist wonderfully with plants and small fish, some need to be intentionally overcrowded just to ensure that they all have multiple targets, to keep wounding at a minimum.

Some ‘classic’ examples of well known cichlids that illustrate the huge variety found within this group are the Oscar, Angelfish, Ram, Pike, Zebra (south American, also known as the ‘convict’ cichlid) and the African cichlids,(there are also ‘zebras’ from Africa ), from the great lakes of Africa. Each of the abovementioned fish has a totally different shape and temperament, and they all reach different sizes as adults, from about 1.5-2” for the Ram, to over a foot for the Oscar. One of things that attract hobbyists to cichlids is their relatively high intelligence, and varied parental behaviors. Most cichlids help to rear their fry initially, and most are excellent parents-watching a pair of cichlids herd their babies around an aquarium, using their respective various signaling mechanisms, is a sight to see indeed. Some even carry the eggs and young in their mouth, in a special pouch, until the young are large enough to try and fend for themselves.


Many people like to have a small tank on their desk, but are limited to a tank size of one to two gallons or less, and wish to keep a fish that is tough, durable, and can tolerate less than ideal water conditions, due to an inability to perform weekly maintenance on the system.

Bettas (originally called the ‘Siamese fighting fish’, because it comes from Thailand originally, and Thailand used to be called Siam) have an adaptation that allows them to do quite well with minimal oxygen levels in the water they live in-they have a special hollow chamber in their head called a ‘labyrinth’ organ, that they can store a bubble of air in, after swallowing it at the water surface. They only need to be kept warm, in clean water, and can be very well maintained in a small (8 oz) desktop container, like a betta bowl, with a weekly water change. Bettas, like the rest of the labyrinth family also construct a bubble nest, and any healthy male betta kept warm (80°F) will spend most of its time building and maintaining this unique structure, providing hours of ‘entertainment’ for their owner.

Marine Aquaria

Marine systems (for the purposes of this article) split into two major groups-fish only, and reef, tanks. Fish only systems can be further split into systems that use man made technology for most of the biological filtration, or natural methods, such as live rock based systems. FOWLR (fish only with live rock) systems are generally more stable and healthier overall, though the end result one gets with either is solely a function of how well the hobbyist does their job.

The knowledge base today on what saltwater flora and fauna require for a happy and healthy life is so vast and freely available that anyone can keep a saltwater tank of any sort with relative ease-you just need the appropriately sized wallet. (A reef tank will cost approximately $50.00 a gallon at the end of the first year-this will go down considerably after that, as part of that figure includes the ‘one time only’ purchases, such as the tank). A nice size reef tank (75 to 180 gallons) will cost about the same as a monthly cable bill to maintain, from an electrical bill perspective.

Saltwater fish have more intense (overall) coloration than their freshwater counterparts. The intense, vibrant color, and wider variety of animal types (in addition to fish, there’s also corals, invertebrates, live rock) make saltwater aquarium keeping a very popular hobby the world over. While more expensive than their freshwater counterparts, as a general rule, the amount of time involved to maintain them properly is really about the same- the expense is different.(saltwater livestock, and the support equipment, is usually higher in price than freshwater livestock, although fish can be found at equally high or low prices in both groups).

Marine ‘Fish Only’ systems

The ‘simplest’ type of saltwater fish aquarium is one that houses only fish. the original configuration for those systems when first kept in the hobby involved using dead corals as decoration, and a high capacity biological (back then, an under gravel, but now generally a ‘wet/dry’, or fluidized bed) filter. It’s now understood and accepted today that accomplishing the same filtration goals via more natural means is a superior long term option-but both natural and ‘artificial’ filtration methods do work perfectly well, for our purposes. As long as the proper environmental parameters/requirements are met, and kept, a saltwater fish only system is no more difficult to maintain than a freshwater one-it just tends to be more expensive, as a general rule.

There are community type setups, both peaceful (read: community) and aggressive (read: predatory).Peaceful does not necessarily mean ‘small’, and aggressive does not necessarily mean ‘large’ fish. Some people keep one large aggressive fish by itself, much like a ‘real pet’. Tank sizes can range from 1 gallon nano tanks to tanks of multiple hundreds of gallons. The filters classically used on these systems is of the ‘wet/dry’ variety, and also usually include an auxiliary device or three, like an ultraviolet sterilizer, and/or a protein skimmer.

Reef Aquaria

This is probably the most rapidly expanding and developing sector of the aquarium hobby in the 21st century. What many considered impossible to do and achieve as recently as 10 years ago in aquaria is now commonplace, with regards to what we can keep in what type of system, and how easily we can keep it. The knowledge base in the reef keeping community is expanding exponentially every year. The reef keeping hobby splits into two major groups, for the most part-regular reef tanks, and ‘nano’ (tiny) reefs. Nano is usually used to designate a tank size of less than 50 gallons, and more typically refers to those below 30 gallon capacity.(there’s also a ‘pico’ class, usually referring to containers of 2-3 gallons or less, and there are currently folks keeping pico reefs in 8 oz. containers! ).

The main attraction is the ability to re-create a miniature ‘slice of the ocean’ in one’s own living room. The variety of life forms, shapes, and colors of livestock appropriate for aquariums is almost limitless, and it is this huge variety that also presents one of the main attractions for folks getting into the reef keeping hobby.

Mini reef aquaria are just as easy to keep today as a ‘standard’ community 10 gallon freshwater tank-the real main difference is one of cost. Almost all reef tanks will cost about fifty dollars per gallon during the first year (this includes the total setup cost, stocking, and operation). That will drop significantly once the system is for the most part stocked with its inhabitants-then it’s a matter of the maintenance costs-replacement salt, testing supplies, supplements, etc.