An all-in-one aquarium is a ready-made kit in which all the elements of the aquarium are designed to fit and work together. For example, the hood that contains the lights fits perfectly onto the top of the tank and has a space for the filter mechanism. The filter is designed to have an appropriate capacity for the amount of water in the tank. The kit also includes a heater, thermometer and substrate (the gravelly material that covers the aquarium's floor).
Some all-in-one aquariums might include extras like a stand suited for the size and weight of the tank. The various electronic components might be integrated by a single power supply, so you just have to plug one cord into the wall to power the filter, heater and lights. Some all-in-ones have an integrated power strip, so you can plug in other devices like powerheads or additional heaters and still use the single wall plug.
At the top end of the all-in-one aquarium spectrum are so-called nano-reefs, or aquariums designed to create a living coral reef in a tank. They usually include water conditioners, salt and salt mixing equipment, testing kits and the reef base, a calcium carbonate substrate that gives various saltwater species places to live and hide.
All-in-one aquariums range from small kits of 10 gallons (38 liters) or so made in designer shapes and colors to large reef systems of 60 gallons (227 liters) or more. They come with affordable, yet heavy glass tanks or lighter, more expensive acrylic tanks. The number of combinations is huge, with lots of choices suitable for novice and experienced aquarists alike. You can find all-in-one aquariums at almost any specialty fish store.
Next, we'll look at the pros and cons of all-in-one aquariums.