A freshwater aquarium is an underwater world for keeping primarily tropical fish whose natural habitats are lakes or rivers. These fish generally need warm water. Depending on the type of fish, the temperatures are between 22 degrees and 28 degrees Celsius. The basic equipment of a freshwater aquarium includes a filter, lighting and heating. Added to this are the flooring in the form of gravel or sand, aquarium plants, cave hideaways made of wood or stone and accessories such as thermometers, nets, feed, fertilisers and care utensils.