From the outdoor ponds and glass jars of antiquity, modern custom aquariums have evolved into a wide range of specialized systems. Individual custom aquariums can vary in size from a small bowl large enough for only a single small fish, to the huge public custom aquariums that can simulate entire marine ecosystems. One way to classify custom aquariums is by salinity. Freshwater custom aquariums are the most popular due to their lower cost. More expensive and complex equipment is required to set up and maintain a marine aquarium. Marine aquaria frequently feature a diverse range of invertebrates in addition to species of fish. Brackish water aquaria combine elements of both marine and freshwater fishkeeping. Fish kept in brackish water aquaria generally come from habitats with varying salinity, such as mangroves and estuaries. Subtypes exist within these types, such as the reef aquarium, a typically smaller marine aquarium that houses coral. Another classification is by temperature range. Many aquarists choose a tropical aquarium because tropical fish tend to be more colourful. However, the cold-water aquarium is also popular, which is mainly restricted to goldfish, but can include fish from temperate areas worldwide and native fish keeping. So go ahead and plant your flora and fauna making your house the most pleasant sight for a relaxing home environment.