Many human beings are tempted to keep fish in isolated artificial ecosystems (aquaria). The motives for that are not very clear and are probably different for each aquarist. In any case, keeping a working aquarium is a real challenge, and probably that is the main reason why people like that hobby.
Since fish cannot live in the same environment as humans, special equipment is needed to reproduce the optimal conditions for them.

Fish stores often sell "all-in-one" beginner kits. However, these are usually not the best solution for your aquarium, and it is better to buy all the items separately if you can spare the time and money.

The fish tank

This is an object, used as a container for the water which the fish are going to be put in. For obvious reasons, it has to be solid and transparent. This leaves us with two choices as far as the material is concerned: glass and acrylic tanks.

Glass tanks

The glass tanks are probably more widely used, mainly because their price is lower. Their other main advantage is that it is harder to make a scratch on them. However, if they are scratched, it is impossible to fix that.

Glass tanks are also heavier, but that is usually not critical.

Acrylic tanks

These are more expensive, but some prefer them. They are more easily scratched, but scratches are easy to fix.

It has to be noted that acrylic tanks do not refract light so much, which means that the inside of the tank will not be as distorted when viewed from a close angle.

Fish tanks come in various shapes, and choosing a shape is entirely up to the aquarist. There are the traditional rectangular tanks, round fish bowls that are suitable for viewing from all sides, corner tanks and more.

Tank size

Size does matter. Although the number of fish that an aquarium can support depends on many other factors, it is quite obvious that a larger tank will be able to hold more fish. 80 litres is a good size for a beginner aquarist. The maintenance of a tank smaller than 40 litres would be too difficult.

Placing the tank

The only important thing you need to remember is not to place the tank where direct sunlight can fall over it. Too much light can promote algae growth, which doesn't look neat in your aquarium, and might be bad for the plants. Another reason is that, of course, your fish could overheat. Other than that, you can place the fish tank wherever you like. Place it at eye level, so that it is easy to watch. Just do not forget that when full, it can get very heavy, so you need a stand that will be able to support it.

Filters

A filter is essential to an aquarium. There are three types of filtration: mechanical, biological and chemical.

The mechanical filtration is basically the process of removing the solid particles floating around in the water in order to keep it clean. This is important, as they would otherwise decompose into toxic substances that are potentially dangerous to the fish.

Filters also host good bacteria that convert such substances to less toxic ones. An effect of the mechanical filtration is that such bacteria are provided with a surface to attach to, running water and enough oxygen. This bacterial colony does what is known as biological filtration.

The chemical filtration is usually not necessary in normally running aquaria and most types of filtration equipment do not include a chemical filtering module.

There are many kinds of filters available. The traditional ones are the corner boxes with the pump which passes water through a sponge. An increasingly popular type is the so-called undergravel filter. Like the name suggests, you place it under your gravel. This way it is hidden away, and looks very neat. For obvious reasons, you'd need gravel if you wanted to use such a filter.

Heaters

Since most fish that are of the right size and colour to be put in an aquarium happen to be tropical, they require an appropriate water temperature and a heater is often needed to achieve that.

The heater also compensates for the temperature difference at night, and it is in fact more important to keep the temperature constant than to keep it optimal.

There also are, of course, coldwater fish¹, which do not need a heater. If you want to keep coldwater and tropical fish in the same tank, you can still try - if you are lucky, you'll have no problems. Fish are cold-blooded animals and their metabolism adapts pretty well to temperatures which are a few degrees off the limits.

For most fish a temperature of around 25C degrees would do well.
To maintain an 80 litre aquarium at 25C, if the room temperature does not fall below 18C (even at night), a heater of about 50 Watts would be enough.

Thermometers

You will, of course, need a thermometer in order to be able to adjust the temperature. Heaters often fail, so the thermometer will allow you to notice that and react timely. There are two types of thermometers: the first is the standard bulb thermometer, which usually hangs from the side of the tank. The other type is the flat liquid crystal thermometer which is stuck to the glass.

Both types of thermometers may be pretty inaccurate, so be advised that the thermometer is only used to make sure that the temperature is not too far off the limits.

Lights

A light is only required if you want to grow live plants in your aquarium (which is recommendable, as plants are an essential part of every ecosystem). Use fluorescent lights, because they do not pose the risk of overheating your aquarium. Be advised that too much light may promote algae growth, so if you have too much algae in your tank, you should probably reduce lighting.

For the best plant-growing results, you can buy a so-calles "full spectrum" light. These lights have a spectrum that is as close to sunlight as possible.

Aerators

This is an air pump, which serves the purpose of increasing the oxygen dissolved in the water. You may not need this if the water surface area is large enough and there is enough water circulation².
Be advised that you can have too much oxygen in the water, so you do not have to install an air pump if you do not need it.

The algae cleaner

When the ecosystem in the aquarium develops, algae may start growing on the walls of the tank. That's when you need the cleaner. It scrubs the algae off the wall. There are some fancy cleaners that have two magnetic parts - you move one on the outside of the glass, while the other one is inside and cleans your tank.

The hood

You will probably want to cover the fish tank with a hood. It reduces the rate of evaporation of the water and prevents the fish from jumping out (and some fish tend to jump a lot). Protection from other things, such as the family cat, is another benefit that the hood brings. It could be made of glass, metal, plastic, wood or some other material.

The siphon

An aquarium needs regular partial water changes, so you should also get a siphon which you can use to easily change water and clean the gravel.

The net

For getting fish in and out of the tank, you need a net. Be careful what net you choose. If it's not the right size, fish may jump out of it or become entangled and get an injury.

Gravel

Gravel is the substrate in a fish tank. You might go without gravel, but it's a good idea to have some for the following reasons:

• It looks good;
• Plants' roots attach to it;
• It is a required filter media if you're using an undergravel filter.

Buying gravel from a fish store is a little more expensive than obtaining it from other sources, but is the best way to make sure that the gravel is suitable for a fish tank.

Whatever you do, it's a good idea to buy a dark-coloured gravel. It usually makes the colour of the fish stick out better.

Before putting it into your fish bowl, here's how to prepare it for use. The process of washing gravel is much like searching for gold:

1. Get a bucket and put the gravel into it.
2. Put in some water and stir the gravel.
3. Pour out the dirty water.
4. Repeat steps 2 and 3 until the water stays clean after stirring.
5. Put aside any gold you found for selling later.

After washing, you could boil it as well, in order to get rid of evil bacteria. However, if you bought it from a fish store, it might have a thin plastic coating -- in that case it shouldn't be boiled.

Decoration

You'll want your aquarium to look good, so it's a nice idea to try your skills as a decorator. Small stones are an all-time favourite. You can make caves out of them, which would be really loved by the fish, as they make a great hiding place.

Make sure that you do not use any sediment rocks for these purposes; they tend to release carbonates into the water, thus making it harder - maybe too hard for some fish.

Other suggestions include driftwood, coloured stones, "No Fishing" signs, treasure boxes, and a backing that you can stick to the outside back of the tank. It can be just black, or any dark colour (for contrast), or it can be a whole underwater scene.

If you take any stones or other decorations from the Great Outdoors (eg a river, lake or mountain stream), boil them for a while first. Otherwise you could introduce algae, bacteria, or parasites into your precious little aquatic ecosystem.

In any case, remember not to decorate too much. You want the attention of a viewer focused to the stars of the show, ie the fish.

That is all the equipment you need to get your aquarium started. Some of the listed items here are absolutely necessary, some are not. In any case, the only other thing that you will need for a working aquarium are the fish (and the water, of course).