An aquarium heater is a device used in the fishkeeping hobby to warm the temperature of water in aquariums. Most tropical freshwater and marine aquariums are maintained at temperatures that range from 22 to 30 °C (72 to 86 °F). The types include glass immersion heaters and undergravel heating. There are also heating mats that may be placed under the aquarium.
Tridacna is a genus of large saltwater clams, marine bivalve molluscs in the subfamily Tridacninae, the giant clams. Many Tridacna species are threatened. They have heavy shells, fluted with 4 to 6 folds. The mantle is often brightly coloured. They inhabit shallow waters of coral reefs in warm seas of the Indo-Pacific region. These clams are popular in marine aquaria, and in some areas, such as the Philippines, members of the genus are farmed for the marine aquarium trade. They live in symbiosis with photosynthetic algae (zooxanthellae). Some species are eaten by humans.
All species in the genus Tridacna are protected under CITES Appendix II.
Tropical fish are fish found in aquatic tropical environments around the world. Fishkeepers often keep tropical fish in freshwater and saltwater aquariums. The term "tropical fish" is not a taxonomic group, but rather is a general term for fish found in such environments, particularly those kept in aquariums.