The general rule is to buy the largest aquarium you can afford and can accommodate in your home. The reason for this is fairly straightforward: Fish require adequate space to swim and sufficient oxygen to live; both are dictated by the size of the tank. The oxygen content of water is related to the surface area of the tank and the temperature of the water. Warmer water has less oxygen than colder water. Since most freshwater tropical fish prefer water warmer than 75 degrees Fahrenheit, the amount of oxygen in the tank may be limited. The more surface area a tank has, the more room for gas exchange at the surface more opportunity for oxygen to enter the water and toxic gases to leave. Therefore, the larger the surface area of the tank, the more fish the tank can hold.
Several different methods have been used to determine fish capacity, and there are several general rules. In my opinion, it is better to err on the side of too few fish than too many fish. Most aquarium enthusiasts use fish length and tank volume to estimate the number of fish an aquarium can hold; larger fish consume more oxygen and, therefore, require more aquarium space. The general rule is 1 inch of fish per 4 gallons of water for the first six months. You can gradually increase fish density to 1 inch per 2 gallons after this initial period. For example, a 40-gallon aquarium should contain no more than 10 inches of fish for the first six months. These may comprise ten 1-inch Neon Tetras or five 2-inch Oscars. After six months, additional fish may be added gradually to increase the total number of inches to 20.
Keep in mind, however, that fish grow, and your 2-inch Oscar may be 3 inches after those six months. Also, realize that this general rule does not compensate for the shape of the fish. The width of a fish is called its girth. The girth of an Eel is much smaller than that of an Oscar, and the 3-inch Eel is likely to require less space than the 3-inch Oscar, so the general capacity rule does not apply. If you plan to keep heavier fish (fish with a greater girth), be more conservative in your tank capacity calculations.
Because surface area is so important to the capacity and health of your aquarium, long tanks are much better than tall tanks. Even though both tanks may hold the same volume of water, the upright (tall) tank has much lower carrying capacity of fish because of its smaller surface area.
Once you have decided on the appropriate size of your aquarium, choosing the tank itself is very straightforward. Home aquariums are made of rectangular glass plates sealed with a silicone rubber cement, or of molded acrylic; both have their ups and downs. Glass aquariums are the most common and practical aquariums to buy, and I recommend them for the beginner. They are built for the sole purpose of housing living animals and are, therefore, nontoxic. Glass does not scratch as easily or yellow as acrylic does.
Aquariums with plastic or metal frames are sometimes available, but I have found that this design is not as aesthetically pleasing and that the frames are unnecessary. When choosing your tank, be sure there are no scratches on the glass and that there are no gaps in the silicone that can cause leaks.
Saturday, April 30, 2011
Friday, April 29, 2011
Fish Breathing
Among the most primary of the basic needs of fish is oxygen. Like land animals, fish require oxygen to live. However, fish must derive oxygen from water and special respiratory organs, called gills, enable them to do so. The gills of a fish are analogous to our lungs: They supply oxygen and remove carbon dioxide from the blood of the fish. Then, oxygen is transported by the blood to the tissues where it is used to produce energy.
Most fish have four gills on each side of the head, protected by a single gill flap, or operculum. When a fish breathes, water is taken into the mouth and passed over the gills and out the operculum. As water passes over the membranes and filaments of the gills, oxygen is removed and carbon dioxide is excreted. To accomplish this, the gills have a very high number of blood vessels that deliver the oxygen to the rest of the fish via the blood.
Most fish have four gills on each side of the head, protected by a single gill flap, or operculum. When a fish breathes, water is taken into the mouth and passed over the gills and out the operculum. As water passes over the membranes and filaments of the gills, oxygen is removed and carbon dioxide is excreted. To accomplish this, the gills have a very high number of blood vessels that deliver the oxygen to the rest of the fish via the blood.
Thursday, April 28, 2011
Fish Feeding
Just as a fish’s body shape can tell you a lot about its swimming habits, its mouth can tell you something about its feeding habits. Bottom feeders have downward pointing mouths, while surface feeders have mouths that point upward. For most fish, the mouth is at the end of the snout.
The size of the mouth is usually directly related to the size of the fish’s preferred food. For example, large predatory fish like Oscars have larger oval mouths for consuming smaller fish. Fish that normally feed on small aquatic invertebrates, like Neon Tetras, have smaller mouths. Some tropical freshwater fish have specialized mouths for specialized feeding strategies. Plecostomus fish, for example, have special sucking mouths for bottom feeding.
Freshwater tropical fish have a relatively straightforward digestive system, which varies from species to species. In general, food passes from the mouth, down the esophagus, to the stomach, and through the intestine; wastes are expelled from the anal vent. However, several species lack true stomachs and instead have elongated, super-coiled intestines.
The size of the mouth is usually directly related to the size of the fish’s preferred food. For example, large predatory fish like Oscars have larger oval mouths for consuming smaller fish. Fish that normally feed on small aquatic invertebrates, like Neon Tetras, have smaller mouths. Some tropical freshwater fish have specialized mouths for specialized feeding strategies. Plecostomus fish, for example, have special sucking mouths for bottom feeding.
Freshwater tropical fish have a relatively straightforward digestive system, which varies from species to species. In general, food passes from the mouth, down the esophagus, to the stomach, and through the intestine; wastes are expelled from the anal vent. However, several species lack true stomachs and instead have elongated, super-coiled intestines.
Wednesday, April 27, 2011
Fish Swim Bladder
As mentioned earlier, living in the dense medium of water presents a few problems for fish, and one of these is buoyancy. Maintaining a certain level in the water column without having to expend a lot of energy is very important to fish. Therefore, most species have a special organ called the swim bladder. This gas filled sac, located in the abdominal cavity of the fish, acts as a life vest, keeping the fish at the correct level in the water column.
There are many types of swim bladders. The Trout has a simple single chambered sac, the Goldfish a two-chambered type, and the Angelfish a three chambered bladder. Different species also use different methods to fill the swim bladder with air. Some have a direct connection between the esophagus and the bladder and simply swallow air to fill it. Others must rely on gas exchange from specialized blood vessels in the circulatory system to fill the swim bladder.
In addition to its role in buoyancy control, the swim bladder helps to mechanically amplify sound for better hearing in certain species of fish.
There are many types of swim bladders. The Trout has a simple single chambered sac, the Goldfish a two-chambered type, and the Angelfish a three chambered bladder. Different species also use different methods to fill the swim bladder with air. Some have a direct connection between the esophagus and the bladder and simply swallow air to fill it. Others must rely on gas exchange from specialized blood vessels in the circulatory system to fill the swim bladder.
In addition to its role in buoyancy control, the swim bladder helps to mechanically amplify sound for better hearing in certain species of fish.
Tuesday, April 26, 2011
Fish Scales
The bodies of most tropical fish are covered with scales. The scales are composed of a hard bony substance and serve to protect the fish, reducing the chance of injury and infection. Covering the scales is a very thin layer of epidermal (skin) tissue that contains mucous cells. These cells produce the slime that we normally attribute to fish. The mucous coating not only protects the fish against injury and infection, but also helps the fish to swim more easily in the water, reducing friction between the body and the water.
The scales of a fish are actually translucent, like glass, and lack color. The vibrant colors of tropical fish come from specialized pigment cells called chromatophores in the deeper dermal layer of the skin. Fish that are clear, like the Glassfish, lack these pigment cells. The color of the fish depends on the types of chromatophores present. There are generally three types of chromatophores in fish: melanophores give fish the darker colors of black, brown and blue; xanthophores produce red, yellow, and orange; and iridophores reflect light, producing a silvery shine common to many fish.
The scales of a fish are actually translucent, like glass, and lack color. The vibrant colors of tropical fish come from specialized pigment cells called chromatophores in the deeper dermal layer of the skin. Fish that are clear, like the Glassfish, lack these pigment cells. The color of the fish depends on the types of chromatophores present. There are generally three types of chromatophores in fish: melanophores give fish the darker colors of black, brown and blue; xanthophores produce red, yellow, and orange; and iridophores reflect light, producing a silvery shine common to many fish.
Monday, April 25, 2011
Fish Fins
All species of fish have fins in one form or another. The fins are critically important appendages that enable the fish to propel, stabilize, maneuver, and stop itself. In some cases, fins have developed to protect the fish as well. Again, depending on the type of fish and the habitat it lives in, the fins can take on many shapes and functions. Bottom, sedentary, or slower moving fish typically have rounded fins, while faster, open water fish generally have longer, pointed fins.
Fish fins are either paired or unpaired. The only fins that come in pairs are the pectoral and pelvic fins, while the dorsal, anal, and caudal fins are unpaired. The pectoral fins are the paired fins closest to the head. The fish uses these fins to stabilize, turn, maneuver, hover, and swim backwards. These fins are generally found just behind or below the gills on each side of the fish, under the midline of the body.
The pelvic fins are also paired and vary the most in position. In some fish, they lie under the fish toward the rear. In others, such as many tropical species, the pelvics are closer to the head under the pectorals. In general, the pelvic fins act as brakes while aiding in stabilizing and turning the fish.
The dorsal and anal fins are unpaired fins that are found protruding from the top and bottom of the fish, respectively. Dorsal fins may be elongated or short, elaborate or simple, singular or multiple. In some species of fish, the dorsal or anal fin may be completely lacking. Both fins help stabilize the fish and keep it moving straight.
The caudal or tail fin is a single fin largely responsible for propelling the fish forward. This fin can also assist in turning and braking. Faster fish have deeply forked caudal fins, while many deep-bodied and bottom fish have square or rounded tail fins.
In general, the main supporting structures of fish fins are soft rays. However, anyone who has handled a fish knows that the dorsal, anal, pectoral, or pelvic fins of many species also have spines. These sharp, bony structures provide protection against predators and can certainly hurt us as well.
Fish fins are either paired or unpaired. The only fins that come in pairs are the pectoral and pelvic fins, while the dorsal, anal, and caudal fins are unpaired. The pectoral fins are the paired fins closest to the head. The fish uses these fins to stabilize, turn, maneuver, hover, and swim backwards. These fins are generally found just behind or below the gills on each side of the fish, under the midline of the body.
The pelvic fins are also paired and vary the most in position. In some fish, they lie under the fish toward the rear. In others, such as many tropical species, the pelvics are closer to the head under the pectorals. In general, the pelvic fins act as brakes while aiding in stabilizing and turning the fish.
The dorsal and anal fins are unpaired fins that are found protruding from the top and bottom of the fish, respectively. Dorsal fins may be elongated or short, elaborate or simple, singular or multiple. In some species of fish, the dorsal or anal fin may be completely lacking. Both fins help stabilize the fish and keep it moving straight.
The caudal or tail fin is a single fin largely responsible for propelling the fish forward. This fin can also assist in turning and braking. Faster fish have deeply forked caudal fins, while many deep-bodied and bottom fish have square or rounded tail fins.
In general, the main supporting structures of fish fins are soft rays. However, anyone who has handled a fish knows that the dorsal, anal, pectoral, or pelvic fins of many species also have spines. These sharp, bony structures provide protection against predators and can certainly hurt us as well.
Sunday, April 24, 2011
Fish Body Shape
A great deal can be learned about a species of fish by looking at its body form or shape. Fish that are streamlined or bullet-shaped, like Neon Tetras, are well adapted to the open waters of freshwater lakes and ponds. On the other hand, flat or stocky fish, like Catfish, typically live on or close to the bottom.
Fish Evolution
The group of aquatic animals that we call fish has evolved over 400 million years to be the most numerous and diverse of the major vertebrate groups (animals with backbones). Fishes have permeated all the waters of the world, adapting with an incredible variety of forms, lifestyles, and behaviors. From seasonal freshwater streams, desert springs, and salty bays to coral reefs and the deep abyss, different species of fish have found and created niches for themselves. There are well over 20,000 known species of fish that currently inhabit the earth, and many are discovered every year.
Since salt water covers more than 70 percent of the earth’s surface and fresh water only 1 percent, one would expect that there would be many more marine (saltwater) species than freshwater species of fishes. Actually, 41 percent of the world’s fishes inhabit strictly fresh water. Although quite similar in many ways to their marine counterparts, freshwater fish have adapted to a much wider range of habitats and a greater variety of water conditions. Hence, freshwater fish are typically hardier than their marine friends and much easier to maintain. That’s good for you.
Since salt water covers more than 70 percent of the earth’s surface and fresh water only 1 percent, one would expect that there would be many more marine (saltwater) species than freshwater species of fishes. Actually, 41 percent of the world’s fishes inhabit strictly fresh water. Although quite similar in many ways to their marine counterparts, freshwater fish have adapted to a much wider range of habitats and a greater variety of water conditions. Hence, freshwater fish are typically hardier than their marine friends and much easier to maintain. That’s good for you.
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