Fish Tanks
Aquarium's range in size from a small glass bowl containing less than a litre through to large public tanks similar to those you might see in an expensive restaurant.
The benefits of a large home aquarium is that they resist rapid fluctuations of temperature and pH, which allows for greater ecosystem stability.
You will also find that an unfiltered bowl-shaped aquarium to be widely regarded as unsuitable for most fish.
In general aquariums should contain three forms of filtration: biological, mechanical and chemical to maintain optimal water conditions.
Biological
Having the right plants in your tank will provide natural filtration of the water and remove bacteria from the floor of the tank.
Mechanical
This typically takes the form of air pumps that run the water of the aquarium through a filtration device. For tanks that don't have many live plants you can also purchase air stones which attached to a pump that will aerate the water. A good sign that there isn't enough oxygen in your water is that your fish will all be swimming close to the surface of the tank.
Chemical
Regular testing of pH levels in your tank is necessary to ensure that the water isn't too acidic or alkaline. Extremes of either with result in your loosing fish.