Here's a quick guide to a few of the terms used by folks who keep fish for a hobby:

• Algae - a green plant that grows on the gravel, walls, and objects within an aquarium.
• Aquarist - a person who keeps aquariums.
• Aquarium hobbyists - a person who keeps aquariums as a hobby.
• Cichlids - a family of fish popular with aquarium hobbyists, cichlids are larger and more aggressive than most other aquarium fish.
• Compatibility - the degree to which different species of fish can peacefully coexist in the same aquarium tank.
• Custom tank - an aquarium, typically of nonstandard size, built to specification for a specific buyer.
• Dechlorinate - to remove chlorine from tap water so that it may be used in an aquarium tank.
• Diatom Filter - a filtration system using diatomaceous earth - an organic sediment with a unique pore structure that will trap debris as small as 1 micron - as the filter media.
• Dorsal Fin - the main fin on the back of the fish. (see illustration below)
• Fry - baby fish.
• Ick - disease caused by a parasite that commonly afflicts aquarium fish.
• Livebearers - fish that give birth to live young.
• Nitrogen cycle - the start-up process for establishing beneficial bacteria in a new tank and in the filter media that convert toxic ammonia to harnless nitrates.
• Pectoral Fins - the fins on either side of the fish. (see illustration below)
• Piscivore - a fish that habitually feeds on other fish.
• Quarantine tank - a small tank where sick fish are kept so they do not contaminate the population of your regular tank.
• Scavenger - any fish that feeds on algae and detritus and in doing so helps keep the tank clean.
• Spawn - the act of fish mating.
• Substrate - the material that covers the bottom of the fish tank.
• UV - ultraviolet - a wavelength component of sunlight.
• Water change - periodic replacement of all or part of the water in the fish tank with new water.