Tropical Fish Secrets
It's always fun when a guest comes into my home for the first time... you can see their eyes light up like a little kids' and exclaim, "Wow, an aquarium!" as they make a "B-line" for it and proceed to gawk in amazement!
Tropical Fish Secrets

Thursday, May 18, 2006

Public aquaria

Public aquaria are facilities open to the public for viewing of aquatic species in aquaria. Most public aquaria feature a number of smaller tanks, as well as one or more large tank greater in size than could be kept by any home aquarist. The largest tanks hold millions of U.S. gallons of water and can house large species, including dolphins, sharks or beluga whales. Aquatic and semiaquatic animals, including otters and penguins, may also be kept by public aquaria.
Operationally, a public aquarium is similar in many ways to a zoo or museum. A good aquarium will have special exhibits to entice repeat visitors, in addition to its permanent collection. A few have their own version of a "petting zoo"; for instance, the Monterey Bay Aquarium has a shallow tank filled with common types of rays, and one can reach in to feel their leathery skins as they pass by.
Also as with zoos, aquaria usually have specialized research staff who study the habits and biology of their specimens. In recent years, the large aquaria have been attempting to acquire and raise various species of open-ocean fish, and even jellyfish (or sea-jellies, cnidaria), a difficult task since these creatures have never before encountered solid surfaces like the walls of a tank, and do not have the instincts to turn aside from the walls instead of running into them.
The first public aquarium opened in London's Regent's Park in 1853. P.T. Barnum quickly followed with the first American aquarium, opened on Broadway in New York. Following early examples of Detroit, New York and San Francisco, many major cities now have public aquaria. Most public aquaria are located close to the ocean, for a steady supply of natural seawater. An inland pioneer was Chicago's Shedd Aquarium that received seawater shipped by rail in special tank cars. In contrast, the recently opened Georgia Aquarium filled its tanks with fresh water from the city water system and salinated its salt water exhibits using the same commercial salt and mineral additives available to home aquarists.
In January 1985 Kelly Tarlton began construction of the first aquarium to include a large transparent acrylic tunnel in Auckland, New Zealand, a task that took 10 months and cost NZ$3 million. The 110-meter tunnel was built from one-tonne slabs of German sheet plastic that were shaped locally in an oven. A moving walkway now transports visitors through, and groups of school children occasionally hold sleepovers there beneath the swimming sharks and rays.
Top public aquaria are often affiliated with important oceanographic research institutions or conduct their own research programs, and usually (though not always) specialize in species and ecosystems that can be found in local waters.
For a partial list of public aquaria worldwide, see list of aquaria.

Sunday, May 07, 2006

Biological loading

Biological loading is a measure of the burden placed on the aquarium ecosystem by its living inhabitants. High biological loading in an aquarium represents a more complicated tank ecology, which in turn means that equilibrium is easier to perturb. In addition, there are several fundamental constraints on biological loading based on the size of an aquarium. The surface area of water exposed to air limits dissolved oxygen intake by the tank. The capacity of nitrifying bacteria is limited by the physical space they have available to colonize. Physically, only a limited size and number of plants and animals can be fit into an aquarium while still providing room for movement.
In order to prevent biological overloading of the system, aquarists have developed a number of rules of thumb. Perhaps the most popular of these is the "one inch of fish per U.S. gallon" rule, which dictates that the sum in inches of the lengths of all fish kept in an aquarium (excluding tail length) should not exceed the capacity of the tank measured in U.S. gallons (about 7 mm per liter of water). This rule is usually applied to the expected mature size of the fish, in order to not stunt growth by overcrowding, which can be unhealthy for the fish. For goldfish and other high-waste fish, some aquarists recommend doubling the space allowance to one inch of fish per every two gallons.
The true maximum or ideal biological loading of a system is very difficult to calculate, even on a theoretical level. To do so, the variables for waste production rate, nitrification efficiency, gas exchange rate at the water surface, and many others would need to be determined. In practice this is a very complicated and difficult task, and so most aquarists use rules of thumb combined with a trial and error approach to reach an appropriate level of biological loading.

Other nutrient cycles

Nitrogen is not the only nutrient that cycles through an aquarium. Dissolved oxygen enters the system at the surface water-air interface or through the actions of an air pump. Carbon dioxide escapes the system into the air. The phosphate cycle is an important, although often overlooked, nutrient cycle. Sulfur, iron, and micronutrients also cycle through the system, entering as food and exiting as waste. Appropriate handling of the nitrogen cycle, along with supplying an adequately balanced food supply and considered biological loading, is usually enough to keep these other nutrient cycles in approximate equilibrium.


New aquaria also do not usually have the required populations of bacteria for the handling of nitrogen waste. In a process called cycling, aquarists cultivate these bacteria as fish and other producers of nitrogen waste are gradually added to the tank over the course of several weeks. Aquarists use several different methods to jump start this process, including the use of water additives containing small populations of the bacteria, or "seeding" a new tank with a mature bacterial colony removed from another aquarium (such as can be found on gravel or biological filter media).
Other cycling methods that have gained popularity in recent years are the fishless cycle and the silent cycle. As the name of the former implies, no fish are kept in a tank undergoing a fishless cycle. Instead, small amounts of ammonia are added to the tank to feed the bacteria being cultured. During this process, ammonia, nitrite, and nitrate levels are tested to monitor progress. The silent cycle is basically nothing more than densely stocking the aquarium with fast-growing aquatic plants and relying on them to consume the nitrogen products rather than bacteria. According to anecdotal reports of aquarists specializing in planted tanks, the plants can consume nitrogenous waste so efficiently that the spikes in ammonia and nitrite levels normally seen in more traditional cycling methods are greatly reduced, if they are detectable at all.
Improperly cycled aquaria can quickly accumulate toxic concentrations of nitrogen waste and kill its inhabitants.

Friday, April 28, 2006

Nitrogen cycle

Of primary concern to the aquarist is management of the biological waste produced by an aquarium's inhabitants. Fish, invertebrates, fungi, and some bacteria excrete nitrogen waste in the form of ammonia (which may convert to ammonium, depending on water chemistry) which must then pass through the nitrogen cycle. Ammonia is also produced through the decomposition of plant and animal matter, including fecal matter and other detritus. Nitrogen waste products become toxic to fish and other aquarium inhabitants at high concentrations.
A well-balanced tank contains organisms that are able to metabolize the waste products of other aquarium residents. The nitrogen waste produced in a tank is metabolized in aquaria by a type of bacteria known as nitrifiers (genus Nitrosomonas). Nitrifying bacteria capture ammonia from the water and metabolize it to produce nitrite. Nitrite is also highly toxic to fish in high concentrations. Another type of bacteria, genus Nitrospira, converts nitrite into nitrate, a less toxic substance to aquarium inhabitants. (Nitrobacter bacteria were previously believed to fill this role, and continue to be found in commercially available products sold as kits to "jump start" the nitrogen cycle in an aquarium. While biologically they could theoretically fill the same niche as Nitrospira, it has recently been found that Nitrobacter are not present in detectable levels in established aquaria, while Nitrospira are plentiful.) This process is known in the aquarium hobby as the nitrogen cycle.
In addition to bacteria, aquatic plants also eliminate nitrogen waste by metabolizing ammonia and nitrate. When plants metabolize nitrogen compounds, they remove nitrogen from the water by using it to build biomass. However, this is only temporary, as the plants release nitrogen back into the water when older leaves die off and decompose.
Although informally called the nitrogen cycle by hobbyists, it is in fact only a portion of a true cycle: nitrogen must be added to the system (usually through food provided to the tank inhabitants), and nitrates accumulate in the water at the end of the process (or contribute to a growth in biomass via plant metabolism). This accumulation of nitrates in home aquaria requires the aquarium keeper to remove water that is high in nitrates or remove plants which have grown from the nitrates. A balanced system, in which the fish eat the plants, is generally difficult to create.
Aquaria kept by hobbyists often do not have the requisite populations of bacteria needed to detoxify nitrogen waste from tank inhabitants. This problem is most often addressed through two filtration solutions: Activated carbon filters absorb nitrogen compounds and other toxins from the water, while biological filters provide a medium specially designed for colonization by the desired nitrifying bacteria.


Ideal aquarium ecology reproduces the equilibrium found in nature in the closed system of an aquarium. In practice it is virtually impossible to maintain a perfect balance. As an example, a balanced predator-prey relationship is nearly impossible to maintain in even the largest of aquaria. Typically an aquarium keeper must take steps to maintain equilibrium in the small ecosystem contained in his aquarium.
Approximate equilibrium is facilitated by large volumes of water. Any event that perturbs the system pushes an aquarium away from equilibrium; the more water that is contained in a tank, the easier such a systemic shock is to absorb, as the effects of that event are diluted. For example, the death of the only fish in a three U.S. gallon tank (11 L) causes dramatic changes in the system, while the death of that same fish in a 100 U.S. gallon (400 L) tank with many other fish in it represents only a minor change in the balance of the tank. For this reason, hobbyists often favor larger tanks when possible, as they are more stable systems requiring less intensive attention to the maintenance of equilibrium.

Source of aquarium inhabitants

Fish and plants for the first modern aquaria were gathered from the wild and transported (usually by ship) to European and American ports. During the early 20th century many species of small colorful tropical fish were caught and exported from Manaus, Brazil; Bangkok, Thailand; Jakarta, Indonesia; the Netherlands Antilles; Kolkata, India; and other tropical ports. Collection of fish, plants, and invertebrates from the wild for supply to the aquarium trade continues today at locations around the world. In many places of the world, impoverished local villagers collect specimens for the aquarium trade as their prime means of income. It remains an important source for many species that have not been successfully bred in captivity, and continues to introduce new species to enthusiastic aquarists.<br>
The practice of collection in the wild for eventual display in aquaria has several disadvantages. Collecting expeditions can be lengthy and costly, and are not always successful. The shipping process is very hazardous for the fish involved; mortality rates are high. Many others are weakened by stress and become diseased upon arrival. Fish can also be injured during the collection process itself, most notably during the process of using cyanide to stun reef fish to make them easier to collect.<br>
More recently, the potentially detrimental environmental impact of fish and plant collecting has come to the attention of aquarists worldwide. These include the poisoning of coral reefs and non-target species, the depletion of rare species from their natural habitat, and the degradation of ecosystems from large scale removal of key species. Additionally, the destructive fishing techniques used have become a growing concern to environmentalists and hobbyists alike. Therefore, there has been a concerted movement by many concerned aquarists to reduce the trade's dependence on wild-collected specimens through captive breeding programs and certification programs for wild-caught fish. Among American keepers of marine aquaria surveyed in 1997, two thirds said that they prefer to purchase farm raised coral instead of wild-collected coral, and over 80% think that only sustainably caught or captive bred fish should be allowed for trade.<br>
Since the Siamese Fighting Fish (Betta splendens) was first successfully bred in France in 1893, captive spawning techniques have been slowly discovered. Captive breeding for the aquarium trade is now concentrated in southern Florida, Singapore, Hong Kong, and Bangkok, with smaller industries in Hawaii and Sri Lanka. Captive breeding programs of marine organisms for the aquarium trade have been urgently in development since the mid-1990s. Breeding programs for freshwater species are comparatively more advanced than for saltwater species.<br>
Aquaculture is the cultivation of aquatic organisms in a controlled environment. Supporters of aquaculture programs for supply to the aquarium trade claim that well-planned programs can bring benefits to the environment as well as the society around it. Aquaculture can help in lessening the impacts on wild stocks, either by using raised cultivated organisms directly for sale or by releasing them to replenish wild stock (Tlusty 203), although such a practice is associated with several environmental risks.
Tropical Fish Secrets
It's always fun when a guest comes into my home for the first time... you can see their eyes light up like a little kids' and exclaim, "Wow, an aquarium!" as they make a "B-line" for it and proceed to gawk in amazement!
Tropical Fish Secrets