Two very different species of fish sell as "angelfish." About a hundred species of saltwater angelfish exist, all of which require advanced care. Three freshwater angelfish exist, one of which shows up regularly in the aquarium trade. While all species of angelfish need aeration, most do not need bubblers. They depend on other equipment that generates sufficient oxygenation as a byproduct of operation.
Aerators are devices that add oxygen to aquarium water. They usually do this by moving aquarium water around. The simplest type of aerator is a bubbler. A bubbler consists of a piece of porous material -- typically a rock called an air stone, though some newer ones are made of plastic or wood -- a length of airline tubing and an air pump. The air pump drives air through the tube into the airstone, which diffuses the air into a stream of bubbles. These increase oxygenation by generating water movement and turbulence at the water's surface via the upward movement of bubbles. While all angelfish require aeration, most angelfish aquariums do not need a bubbler, since angelfish require real filters, which create sufficient aeration for them.
Types of Filtration
Filtration is more important to keeping angelfish alive and healthy than aeration. Aquarium filters need to provide three types of filtration: mechanical, biological and chemical. Mechanical filtration -- physical straining of debris from the water column -- is simplest and of least importance. Biological filtration is the action of bacteria breaking down fish waste. Chemical filtration is the use of substances like activated carbon or zeolite to absorb toxic compounds like ammonia and nitrite from the water. In most aquariums, biological filtration is the most important type of filtration since it is a long-term process that keeps the tank stable. However, the two more rare freshwater angelfish prefer water acidic enough to inhibit the bacteria that break down fish waste. So, in their tanks, chemical filtration is paramount, so replace carbon and zeolite inserts regularly.
Types of Filters
Some filters provide all types of filtration, and aeration as a side-effect. These include the power box, the canister and the sump filter. Power box filters are the cheapest of the triad. These filters that hang on the back of the aquarium and provide all three types of filtration depending on the media inside. Canister filters are similar, except they are more powerful and they connect to the tank through tubing, making it easier to keep them out of sight. Sump filters take this a step further; they consist of a separate container of water, often a smaller fish tank, full of baffles, filter media and other equipment. All types of filters can work for both freshwater and saltwater aquariums, though sump filters are more common in saltwater tanks.
There is one situation whereby angelfish may need a bubbler. With freshwater angelfish, some hobbyists prefer to care for the eggs without the parents. While freshwater angelfish are unusually good parents for a fish, sometimes inexperienced breeding pairs goof up and eat their eggs. However, when caring for eggs, you need to provide gentle, constant water movement to keep them alive. A bubbler suspended just above the eggs -- so the water movement moves across them but does not actually blow bubbles onto the eggs -- can act as a surrogate for the parents' constant attention. This is the only time angelfish need a bubbler.
- Stockbyte/Stockbyte/Getty Images