A Few Fascinating Fishy Physiological Facts

By Kathleen Rader, Colorado Aquarium Society. Note: originally published in the 1990 Spring/Summer issue of “The Colorado Aquarist”.

Migdalski and Fichter wrote an interesting book entitled The Fresh and Salt water Fishes of the World (1976, Knopf Publishing, 316 pp). They covered every modern family of fish, and also discussed fossil fish, taxonomy, and so on. A distillation of some of the physiology is given below.

Scales: As a fish grows, its scales increase in size, but not in number, although most species of fish are capable of replacing lost scales. The ridges and spaces on some scales can be studied like the annual rings of trees. Scale experts can tell the age of the fish, when it first spawned and the timing of every subsequent spawn, periods of food scarcity, timing of migrations, illness, etc. Only a few scales are needed for this type of study. Vertebrae and associated bones also have growth rings, but the fish must be posted to study them.

Dragonets

by Kathleen Rader, Colorado Aquarium Society. Note: first published in the Autumn, 1990 issue of “The Colorado Aquarist”

If you are looking for a small fish to put in your invertebrate, seahorse, or other salt water tank, take a close look at these little fish. Their natural curiosity, hopping motions, and ability to get in and out of very small crevasses will add spice to your tank watching, not to mention the addition of wild color patterns by some of these species.

Dragonets belong to the Callionymus family, which contains approximately eight genera and over one hundred species, all of which are marine. The four species most commonly seen in the United Sates belong to the genus Synchiropus, although some have been misnamed “goby” or “blenny”. Callionymus lyra, from the temperate waters off Europe, is one of the pioneering fish in marine aquarium keeping, their spawning behavior has been known since the 1800′s.

Poem: Hermit Crabs

By Kathleen Rader, Colorado Aquarium Society. Note: first published in 1988 in issue No 3, of “The Colorado Aquarist.

Have you ever kept a small hermit crab?

About them I’d like now to blab.

        If you overfeed your tank,

        These crabs you can thank,

As they eat everything they can grab.

Fossil Fish

By Kathleen Rader, Colorado Aquarium Society Note: originally published in the 1989/1990 Winter issue of “The Colorado Aquarist”.

Fish were the first animals with a backbone (vertebrates) to evolve. They appeared in the Ordovician (500 million years before present), evolving from an unknown phylum of invertebrates. Fish ancestry is uncertain, but there are few missing links in the fossil record from the first fish to mammals.

The oldest fish fossils are from Ordovician formations in the U.S.S.R. and Colorado. Pieces of the oldest fish were collected a few miles north of the state penitentiary in Canyon City from the Middle Ordovician Harding Sandstones. Lucky collectors can find small bony scales at this locale.

JAWFISH

By Kathleen Rader, Colorado Aquarium Society.  Note: originally published in the early 1990’s in “The Colorado Aquarist”.

Smilers, Monkeyfish, and Goggle-eyed Cods are all names which have been given to these compulsive burrowers. In scientific nomenclature, jawfish belong to the family Opistognathidae, which contains three genera: Opistognathus, Lonchopisthus, and Stalix. Only the first two are commonly kept in saltwater aquariums. These fish are closely related to pygmy basslets and fairy basslets.

Jawfish are found in tropical to temperate waters around the world. At least eleven species live in the western Atlantic; eight of these are known to reside along the east coast of the U.S. They also inhabit the Florida Keys area, the Caribbean, Gulf of California (Sea of Cortez), Pacific, the east coast of Bali in the Indonesian Ocean, and the Great Barrier Reef of Australia. Unlike pygmy basslets, jawfish prefer living in flat, sandy or coral rubbled areas associated with coral reefs.

The Graceful Seahorse – A Unique Fish

by Kathleen Rader, Colorado Aquarium Society. Note:  first published in the early 1990’s in “The Colorado Aquarist”.

In Medieval times, seahorses were dipped in wine and fed to condemned prisoners as a deadly poison. Some believed that the ashes of seahorses, when combined with honey and vinegar, would cure most illness. Living seahorses dipped in oil of roses were supposed to be good for chills and fever; others used them as aphrodisiacs or to cure baldness. Today, the seahorse is kept in home aquariums to relieve stress.

Habitat: People are surprised to learn that seahorses live in water as far north as Norway. They are found in the Atlantic, Pacific, Indian and Southern Oceans, the Gulf of Mexico, Caribbean, Red Sea, Black Sea, North Sea, Mediterranean and the English Channel. Most seahorses reside in heavily vegetated areas of seaweed, turtle grass or eel grass, in shallow coastal waters that have a sandy or muddy bottom. They are also found in masses of floating seaweed (i.e. sargassum) which can carry them hundreds of kilometers. A few specimens have been retrieved from depths of 600 feet (183 m). They are found in normal marine to brackish (up to 40% fresh) water at temperatures of 43-86oF (6-30oC).

Common Aquarium Bunch Plants

by Kathleen Rader, Colorado Aquarium Society. Note: originally published in the early 1990’s in “The Colorado Aquarist”.

Stores often sell what they call bunch plants. These usually consist of a bundle of plant stems that are held together by a rubber band or lead weight. They are propagated as cuttings. When they become too tall, or thick, they can be pruned back and the pruning pieces can be replanted.

To plant most bunch plants, break the ends off to give the stem a fresh cut, strip the lower inch or so free of leaves and plant them into the gravel. It is usually best to anchor the recently planted cuttings to give the roots a chance to develop. Each plant should be slightly separated from the bunch so that light and water can reach the stems and leaves at the base of the plant.

Back to Basics: Lighting the Tank

By Kathleen Rader, Colorado Aquarium Society. Note: Originally published in the “Summer 1991” issue of the “Colorado Aquarist”.

In nature, the sun supplies the light that life requires. Before deciding on how you will provide your captive friends with adequate amounts of this vital form of energy, it is important to know what types of organisms you are keeping, where they come from in the wild and how dependent they are on specific forms of light.

The least expensive lighting fixtures use incandescent bulbs. The bulbs are cheap and easy to replace, unfortunately they also put out a lot of heat. When the light is on, the water is heated, when the lights go out the tank cools off. This is especially true for smaller tanks, since smaller volumes of water heat up and cool down much more quickly than larger volumes. Such fluctuations in temperature will stress the fish and make them susceptible to diseases such as ich. This is especially true of tropical fish which do not tolerate a temperature difference o more than a few degrees between day time and night time.

Back to Basics: Tank Maintenance

by Kathleen Rader, Colorado Aquarium Society. Note: originally published in early 1990’s in the “The Colorado Aquarist”.

You feed your fish every day, so take a minute to notice what is going on with the tank. Check the temperature and aeration and look for dead or unhealthy fish or plants. Early detection of a problem may prevent the loss of an expensive or favorite fish. You may want to jot down what you observe in a notebook. Keeping notes on what fish and plants you have in each aquarium, what the water conditions are, how the fish behave and interact with each other, etc., may help you when you are trying to determine their sex, breed them, decide who a bully in the tank may be, etc. It can also be an interesting record on all of your fish keeping experiences, and how it has changed with time.

Keeping healthy fish means that you must do regular partial water changes. This means establishing a routine and keeping with it. Partial water changes are how you remove nitrate and salt build ups. Some people like to do frequent, small water changes (10-20% of the water every week). Others prefer doing a greater percent of the water each time (20-30%) but do it less frequently, such as every other week. On very young or sick fish, many people will do water changes once or twice a day or more. Whatever you choose to do, establish a routine water change schedule that works best for you and your fish and stick with it. Your fish will thank you by being healthy and happy.

Back to Basics: Heating the Tank

by Kathleen Rader, Colorado Aquarium Society.  Note: originally published in early 1990’s in the “The Colorado Aquarist”.

Fish must be housed in water that is a suitable temperature, that replicate their native habitat. Keeping fish at an inappropriate temperature or in tanks where the temperature fluctuates a lot, will stress the fish leading to disease. Knowing what type of fish you are keeping will help you know what conditions to provide them with.

Goldfish, koi, many killifish, some native fish do best in water that is room temperature or slightly cooler. The temperature should not fluctuate too much on a daily basis, although seasonal fluctuations are usually tolerated by most of these fish. Keep the tank away from sources of sunlight, air ducts, and open windows. These tanks do not require a tank heater.

Back to Basics: Aeration and Filtration

By Kathleen Rader, Colorado Aquarium Society. Note: originally published in the Spring 1991 issue of “The Colorado Aquarist”.

Fish use their gills to take oxygen out of water. They release carbon dioxide as a waste product. The amount of oxygen in the water that is available for fish to “breathe” is a function of the temperature of the water, the amount of organisms using oxygen and how much air is in contact with the water. Without artificial means of aeration, the amount of surface area on the top of the tank (where the water is in contact with the air) is the major factor in how much oxygen goes into the water and how much carbon dioxide comes out. Without sufficient levels of oxygen in the water, fish can suffocate. Most filtration methods have some component of aeration which causes water to come into contact with air; either a current is established to move the water to the surface, or bubbles of air rise through the water column. This increases gas exchange, providing more oxygen for the fish.

There are three types of filtration: biological, mechanical and chemical. In biological filtration, bacteria living on the filter medium break the fish waste product ammonia (very poisonous to fish) down to nitrite (also a poison to fish) and other bacteria break the nitrite into less harmful nitrate which can then be removed by partial water changes. All aquariums need some type of biological filtration to maintain proper conditions for keeping fish alive and healthy. Mechanical filtration is the physical removal of debris such as dead plant material, solid waste material, etc. Chemical filtration is the removal of some type of chemical and is usually used to remove a medication or conditioning chemical after a special treatment has been completed.

Back to Basics: Tank Selection and Location

By Kathleen Rader, Colorado Aquarium Society. Note: originally published in early 1990’s in the “The Colorado Aquarist”.

Deciding on the size of tank one wants is the first, and maybe the most important, step in selecting an aquarium. Larger tanks are more expensive and take up more room, but for most fish, bigger is better. This is because larger tanks hold a much greater volume of water–the larger the mass of water, the more slowly it will fluctuate in temperature and water quality. Small tanks can go “bad” very quickly, from such things as a bad thermometer, dead resident or poor tank maintenance. Additionally, a larger tank can give the “little fish” bought at a store more room to grow up to its “big” adult size, especially when dealing with fish like angels and other cichlids. Ten gallon and smaller tanks work well, as long as they are monitored and cared for on a regular basis, and the fish population is kept on the small scale, such as most tetras, barbs, killifish, danios and livebearers.

The shape of the tank is also important. The more area of air-to-water contact, the better exchange of gases. Shorter, broader tanks are the best. The tall and extra tall show tanks, hexagonal and half hexagonal tanks may fit better with your room’s decor, but they are limited in the amount of air/water contact. These types of aquariums should have extra sources of air bubbling through them to help enhance the exchange of oxygen into the water and carbon dioxide out of the water. Not only do tall tanks have a problem with gas exchange, but lighting is also a problem. The water column filters out light, so in taller tanks, little or no light reaches the substrate from conventional, over-the-tank light sources. Live plants do not do well in these tanks unless extra light is given, either by submersible lights or spot lights shining from the side of the tank.