O - Aquarium and Fish Dictionary

Aquarium Fish Definition and Glossary

Odontode :: external "teeth like" growths near body openings found on some fish species like the catfishes.
Omnivore :: is an animal or fish that eats both meaty and plant like foods.
Oodinium :: is the freshwater version of the parasite that causes velvet disease.
Osmoregulation :: is the process fish use of regulating the concentrations of salts (ions) and water across a semi-permeable membrane (the gills) through osmosis and diffusion. As a very over generalized example, there is a much greater amount of salts in the ocean than in the saltwater fish's body and saltwater fish would dehydrate quickly if not for their specialized gills that can remove salts from the water.
Overflow Box :: a piece of equipment that hangs on the back of the tank that is used to drain water from the tank into a sump type setup. Hobbyists that don't have a pre-drilled tank for running a closed loop circulation system or sump utilize an overflow box to get the water from the tank and into the closed loop or sump.
Oxygen :: Just like humans fish need oxygen for respiration. Fish take oxygen out of the water using their gills. Oxygen is dissolved in the aquarium water at the water surface. If oxygen levels drop too low, fish may suffer and even die. To increase the oxygen level in your aquarium, use a powerhead directed toward the water surface to cause agitation. Air stones (attached to an air pump) can also cause water surface agitation, thereby increasing the dissolved oxygen levels. Also know that cooler water can carry more oxygen than warmer water and avoid overcrowded conditions (stock lightly).
Ozone :: O3, is a very unstable gas that is sometimes used to increase the dissolved oxygen content in aquarium water and in conjunction with saltwater protein skimmers in order to increase skimmer output.