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Life in a Fishbowl:
The Science and Art of Fishkeeping

Peter Lodenquai
Quality Control Analyst
Quality Control Clinical Development Department
Genentech, Inc.

My First Aquarium...

How many times has this happened to you? You go to a local carnival and play that game where you try to throw ping-pong balls into little brandy glasses on a table. If your ball gets into one of those glasses, you win the prize - a bright orange goldfish swimming around in a tiny cup of water. So, you take the fish home in a plastic bag and when you get to the house you realize that all you have to put it into is a large mayonnaise jar. You wash out the mayonnaise jar, fill it with cold tap water and pour the fish in. Now it's swimming around in the jar as happy as can be!! You might even add some bread to give it food, but you notice it is not eating. It's getting late so you go to bed wishing the fish "good night". The next morning you find what typically happens to thousands of these ping-pong carnival goldfish each year: it's now swimming near the top of the water and slowly gasping for air. It is definitely not looking healthy! To make matters worse, the bread you had put into the jar the night before is all soggy and the water is turning cloudy. A few days later, the fish is floating belly up with a wide goggle eyed stare, quite dead to say the least!! I really wonder how often this story repeats itself across America!

My Introduction to Science

I've been interested in fish since I was five years old and I regret to say that I've been guilty of the very scenario described above numerous times in my life. But, over the years, my fascination with fish and aquariums has led me to learn a lot about the art of fish keeping and the science that goes with it. In this article I'd like to discuss with you some of the aspects of fish keeping and how this hobby relates to scientific disciplines as chemistry, animal physiology, biochemistry, field ecology and even microbiology. For convenience this article will only discuss freshwater systems.

A Natural Environment

A healthy freshwater pond, lake, river or stream is a rich habitat with a delicate ecological balance of living organisms. Water quality, food, shelter, temperature and a wide variety of other factors all play a role in maintaining this balance and allowing the flora (plants) and fauna (fish and other animals) to thrive. A good aquarist attempts to recreate those optimal conditions of the natural ecological balance when building an aquarium habitat or biome. Of course we must remember that there are always some significant differences between a natural habitat and an aquarium. Perhaps the most significant is that ponds, small streams, lakes and rivers are open systems while a fresh water aquarium is a closed system with many limitations. Why would we attempt to recreate natural environmental conditions in the "artificial environment" of an aquarium? Because, in most cases, the natural environment represents the most optimal balance of factors necessary for a healthy living system.

Species Selection

The first important factor to consider is choice of the species or combination of species that will live in your aquarium. This is called species selection. One must know the water conditions each species needs, species compatibility, appropriate food sources, etc. For example, you would not want to set up the predator-prey conditions of the natural environment in the aquarium and then expect it to thrive. A school of neon and cardinal tetras, which are about an inch long, would not go too well with a ten inch long Oscar which can have quite an appetite! Your tank would soon go from a community to a single species aquarium containing one satisfied Oscar! Another example to avoid would be the following: An African Rift Valley Cichild which needs hard water and has a territorial temperament is not compatible with a few South American Angelfish, which need soft water and are of mild temperament. The African Cichlids would tear the Angelfish apart! In our opening goldfish example, the common goldfish was chosen. As a single fish swimming in a mayonnaise jar, the predator-prey conditions are not a concern.

Tank Selection

Next, a fish tank needs to be selected. In the natural environment, fish have space to explore and some species set up territorial domains. To emulate nature, a simple rectangular glass tank of five or ten gallons is a nice size with which to start. Similar to the natural environment, there is a good surface area/air ratio allowing the exchange of gases between the water and air. A tall, hexagonal tank should be avoided because there is not the good water surface area to air ratio as described above. For the aquarist an aquarium made of glass or plexiglas/acrylic allows for good viewing of your fish. If you have a choice between two sizes of aquarium tanks, choose the bigger one. Large aquariums do not fluctuate in temperature as readily as small ones. Most fish can withstand small changes in temperature. Large changes in temperature can put the fish into shock. See below under temperature.

Space

How much space do the fish need? One good rule of thumb on space is to have one gallon of water per inch of fish in the tank. Fish need sufficient space to move around. Often fish in the natural environment establish a domain of a certain size. An overcrowded tank is a source of trouble in addition to the fish's health. Oxygen levels run low and waste buildup is inevitable. Mechanical filtration and partial water changes although helpful, still cannot make up for overcrowded conditions. Ever seen fish gulping water at the surface of the tank? This is because in a low oxygen level tank, there is a greater amount of oxygen in the water at the water/air interface. An airstone and pump can help solve this problem but it is better to match the number of fish to the number of gallons of water in the tank.

Here's an interesting note about fish in the wild as long as we're talking about overcrowded conditions. It has been long noticed that in overcrowded bodies of water such as a farm pond, all the fish will often be stunted. In other words the fish will be less than the normal expected size and weight for that species. Have you ever fished at a small pond full of bluegills only to spend the whole day catching runts? This occurrence is due to the fact that in overcrowded bodies of water the fish only grow in proportion to their nutrient intake, i.e., too many competing fish deplete the available food sources. Of course in an artificial environment such as your aquarium you can always add more food but overcrowded aquariums are more prone to disease conditions, stressed fish and other problems.

Temperature

The type of fish selected determines such conditions as optimal temperature and water chemistry needed. When selecting the tank one option is to choose one with a heater for fish with a relatively high temperature requirement. Different species of fish require different ranges of temperature depending on their natural environment origins. Goldfish come from the carp family and are adapted to living in water with temperatures between 32-68 degree F. These fish can therefore live comfortably in water which ranges from room temperature to very cold. In nature, as the season's change the water temperature drops gradually. This same principle applies to our goldfish. Let's suppose the temperature of the water in the bag that you brought the fish home in was 60 degree F. When the fish was poured into the mayonnaise jar full of cold tap water (50 degree F) it went into shock! It would have been better to leave the bag with the goldfish next to the mayonnaise jar of water for several hours so that the two bodies of water could arrive at the same temperature. In that event there wouldn't have been a temperature element of surprise for our poor fish awaiting its fate in the bag. Another point to keep in mind is make sure your fish tank is away from any windows. Major fluctuations in tank temperature due to sun warming in the day, or chilling in the evening by a cold draft, can occur. In the natural environment, a fish has a larger body of water so it can swim to the bottom to move away from frequent temperature changes found on the surface.

Water Chemistry

Some of the other factors of water chemistry that are important for an aquarium are pH, water hardness, nitrite/nitrate level content, and oxygen and carbon dioxide concentration. Each species has a optimum range in nature . Also, since our aquarium is a closed system these conditions must be monitored frequently. Let's take the first case of acidity, otherwise known as pH. The pH is a measure of the relative acidity of the water. The pH scale ranges from 1 to 14 with pH 1.0 being the most acidic to pH 14.0 being the most basic. For most freshwater fish the optimal pH range is pH 6.0-9.0. I've found that the tap water where I grew up was in the alkaline range of pH> 7.0. I could test the pH of my aquarium with litmus test strips or with a pH test kit which has a color indicator that changes to shades of blue in the alkaline range, green in the neutral 7.0 region and shades of yellow in the acidic range. To correct the pH, either acid or base can be added to the water. Please note that a change in one degree of pH represents a 10 fold change in acidity. Therefore, any corrections for desired pH must be done gradually over time. It is possible that the difference in pH of the water in the bag as compared with the water in the jar played a role in sending our poor goldfish into shock! In order to overcome this pH difference between the water in the bag and the water in the jar, slowly add the mayonnaise jar's water into the bag to allow the fish to adjust to the new pH.

Water Hardness

Water hardness is the measure of mineral salt concentration present in the water. Most important among these dissolved minerals are calcium and magnesium carbonates. In our case we are concerned about the amount of carbon dioxide in the water which is in the form of carbonic acid and carbonate. Carbonate hardness is the measure of carbonate concentration in the water. Carbonate hardness affects the pH of the water which is directly related to the concentration of free carbon dioxide. Most aquarium fish will thrive in medium to hard water. Water hardness test kits are available in most aquarium stores. To change the hardness of the water in your tank, one can use a peatmoss filter, ion exchange filter or add distilled water.

Nitrogen Cycle

Fish excrete waste products such as urine which, when converted to ammonia, is toxic. Because ammonia (NH3) is a gas it rapidly becomes solubilized in water and ammonium ions(NH4+) are formed. Ammonium ions are used by bacteria and plants for amino acid synthesis. In both natural environments and aquariums, bacteria of the genus Nitrosomonas live in the soil, gravel, rocks and sand. These organisms obtain energy by oxidizing ammonia to form a toxic product called nitrite(NO2-). In a healthy aquarium and in nature, this nitrite can be converted into harmless nitrate (NO3) by nitrogen fixing bacteria, Nitrobacter, in the process of denitrification. It takes several weeks for an aquarium to build up the necessary amount of nitrogen fixing bacteria. This demonstrates the fine balance of the ammonia/nitrite/nitrate levels which can be monitored with a nitrate test kit in an aquarium. The nitrogen cycle is common to all aquariums and nature. In order to avoid nitrate toxicity, it is crucial to make sure the aquarium is not overcrowded, with excess fish excrement on the tank floor.

Live Plants

One tip to help the quality of the water is to use live plants which not only use up waste nutrients but also make the tank more appealing. Of course, the use of live plants depends on the temperament of the fish you intend to keep. In nature, there is a balance between the fish and the plants in that area. In the aquarium the aquarist wants the fish to be compatible to the plant life. If not, some fish will shred the plants. Live plants have a number of requirements such as light, nutrients and good water quality. A good indicator of how good the water quality is in your tank is to look at the plants! Some plant nutrients such as iron can be added to the water. These additives help the plants grow significantly better. I have a friend who keeps a 20 gallon plexiglas tank with beautiful amazon sword plants with African butterfly fish. The secret to his tank is good maintenance and using nutrients to help his plants. Please note that plants in the presence of the correct wavelengths of light will produce oxygen via photosynthesis but in the absence of light use the oxygen they produce!

Filtration

In nature filtration occurs naturally in open systems. Filtration removes unwanted debris such as fish excrement, dead plants and other extra elements that may cloud the water. Good filtration is important to the health of your aquarium. There are many kinds of filtration available but I suggest either or a combination of two types. These are the outside box filter or an undergravel biological filter. These filters will create a gentle current in your aquarium which is good for the overall health of the aquarium. The box filters hang on the outside of your tank and remove excess food and other particles. They are relatively inexpensive and are very easy to clean. Natural filtration can be replicated in an aquarium by using an undergravel filter. These filters keep water moving through the gravel and allow a good population of nitrogen fixing bacteria to thrive. A combination of both the outside box filter and undergravel filter will keep the tank clean and fresh along with partial water changes which means changing approximately 20% of the tank's water about every two weeks. Try to stay away from purchasing the inside box filters. Although they are inexpensive, they tend to get clogged easily and do not work efficiently. The floss, which is the fluffy nylon material from the filter, goes floating all over the place and the air tubing gets disconnected. This causes a mess to the entire cleaning process. Also, reaching into the tank to clean those inside box filters can scare the fish.

Other Factors to Consider

Some of the other general things one should keep in mind when setting up an aquarium are: What depth of the pond, lake or stream do these fish live at in the wild? (top, middle or bottom), What kinds of food will they require? Are there territorial concerns?

Determining ahead of time what the needs are for the aquarium you would like to establish and deciding whether or not you can provide them can save the aquarist a lot of needless frustration and anxiety.

There is the question of whether to choose glass or plexiglas/acrylic aquariums. More people seem to be choosing plexiglas/acrylic over glass aquariums. Plexiglas/acrylic tanks are lighter and stronger than glass tanks but care must be taken because they scratch easily. Also note that they happen to be slightly more expensive than their glass counterparts.

Be a Naturalist!

One interesting thing you can do is collect your own fish locally and maintain them in your aquarium. Check with local regulations before doing so. There are many advantages to collecting your own fish: First of all it's a lot of fun! Second, you know what the conditions are for these fish in the wild and you can attempt to recreate them. The cost is minimal and the collecting trip is a great learning experience as well as a great day outdoors! You can use a net to catch small minnows or use light fishing tackle with small hooks to catch sunfish. A few small bluegills, pumpkinseed sunfish, or redear sunfish in the right sized tank can teach you a lot about fish behavior and allow you to observe them more closely. I maintain a few wild redear sunfish in a small 5 gallon tank at home. I feed them live redworms, live brine shrimp and freeze dried bloodworms. These foods are available at your local aquarium dealer or even better: Catch your own! A few small earthworms and some bugs from the backyard make great fish food for your wild caught fish! The fish are accustomed to these kinds of food as you might notice it is often difficult to get them to eat flaked foods.

In Conclusion

In the brief space we have here it is impossible to discuss in depth what volumes of aquarium books contain concerning the care of fish and aquarium systems. I've included a list of suggested aquarium literature you might want to look up in your local library or aquarium store. Many of the references listed give discussions on what fish need to remain healthy in its aquarium environment. In an aquarium, the fish are dependent on the aquarist to provide what its natural environment maintains that is the right food, light, shelter, partial water changes, etc.

The poor goldfish in our first example would have stood a chance to live if it was provided the right conditions. Knowing some of the basics of fish keeping and putting them to practice can bring hours of satisfaction in the form of a well maintained aquatic environment. I think it is better and more relaxing than television! Fish keeping is a science and art that the aquarist can practice for many years.


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