Tips for Healthy Aquarium Inhabitants: Preventive Measures for Aquarists, Part One

by | Jan 15, 2009 | 0 comments

One of the hallmarks of a good aquarist is practicing preventive measures. Experienced hobbyists usually realize how important these habits are to their long-term success. Prevention consists of more than merely quarantining newly acquired fish. It also includes researching animals prior to purchase, making wise choices and being prepared in the event of an emergency. Practicing these good habits will minimize stress, prevent injury and insure that your stock will be well nourished.


Good things take time, but bad things can happen quickly in this hobby. That is why patience is such an important virtue for aquarists. While preventive measures do take some time and effort they also save time in the long run. One may think that it is easier to skip quarantine so they can get fish into the display aquarium quicker, but taking such risks often results in lengthy setbacks. This can mean losing stock to contagious disease or parasites. How much time is actually saved if all the fish have to be removed to another tank for treatment, because the proper steps were not taken to prevent an infectious disease from entering the display aquarium?

Six weeks of quarantine is recommended for recently captured reef fish. This allows enough time for them to regain their health, recover from the stress, adapt to captivity and learn to eat new foods. All newly acquired fish should be quarantined in isolation from other animals for a minimum of thirty days, regardless of the conditions that they came from. Exceptions can be made for mated pairs or small groups of shoaling fish to share a quarantine tank.

A quarantine system may be the best investment that an aquarist can make. Not only will it save money in the long run, it will save time and help you to avoid heartbreaking situations. Medicating a display aquarium may destroy the biological filtration and the invertebrates, as well as the fish, may not survive the treatment. Using a quarantine system will help you to steer clear of many situations that may make it tempting to medicate the display aquarium.

An efficient quarantine system does not require a sizable financial investment. All that is really necessary is a tank or food grade Rubbermaid™ container, a heater, some PVC pipe for hiding places and a something to provide biological filtration. An outside filter with a biowheel, or a sponge filter driven by an air pump will suffice. Don’t forget to use a lid or screen to keep the fish from ending up on the floor. Overhead lighting is optional for fish, while some invertebrates require intense illumination. Place the isolation tank in a quiet location away from the main traffic flow of the house.

Do not keep rock, substrate or other calcareous materials in a quarantine system. It is better to rely on a filter that can easily be removed or replaced for biological filtration. Some medications may destroy or inhibit the bacteria that perform nitrification and calcareous materials will react with copper to take it out of solution.

Stable water conditions are important to the health of all fish, especially those that have been recently exposed to stressors. Keep a cycled quarantine tank up and running at all times so you won’t have to deal with ammonia poisoning or unstable water parameters.

At times it may be necessary to sterilize the quarantine tank after finishing treatment for a contagious disease or parasite. This can be accomplished by adding a little chlorine to the water for a few hours. Then remove the chlorine and change the water. Keep a spare sponge filter or biowheel in the sump of your display aquarium so you always have a backup biological filter ready for use in your quarantine system.

The water parameters should be monitored closely in a quarantine system. Keep test kits for ammonia, pH, alkalinity, copper, oxygen, nitrate and nitrite near the aquarium. Regular, weekly water tests will help you keep track of the water parameters. Record a log of the results so any trends, such as a falling pH, will become evident. Don’t forget to check the expiration dates of your test reagents to insure accurate readings.

An easy to read thermometer should placed in or on the aquarium. Use two small heaters rather than one that is powerful enough to overheat the aquarium. This is safer in the event of a malfunction. One small heater can’t overheat the aquarium while it will prevent the water temperature from falling quickly if the second small heater stops working.

Do not use the same nets, cleaning equipment, etc., for your quarantine and display aquarium. It is not worth the risk of spreading a contagious disease or parasite. Use a food-grade Rubbermaid container when you give your fish a freshwater or medicated dip. Don’t forget to use a ground fault interrupter and to turn off the power whenever working on your aquarium. Just in case you might forget, a timer can be used to automatically turn the power back on after you have finished.

Plastic swing-arm type hydrometers will work well enough provided you don’t need to measure the salinity precisely. If you ever need to treat your fish with hyposalinity therapy then an accurate means of measuring the salinity is essential. A refractometer is a good investment and more accurate than most hydrometers.

Observe the animals in quarantine daily for any changes in behavior or visible symptoms of disease. Check the respiration rate to see if it is accelerated, normal, or abnormally slow. Are the eyes clear? Are they eating and showing an interest in their surroundings? Do they rub against objects in the aquarium? Is the fish swimming normally and using all of the fins? Is their coloration bright or faded? Do they react to your approach? While it is essential to closely observe the specimens in quarantine don’t do it several times a day, because this may cause stress for the animals.

To get a good look at a fish in the aquarium trap it against the glass with a specimen container or net. Then look them over closely using a magnifying glass and a flashlight. This should make it easier to identify any potential visible symptoms. Have at least one book that you can refer to that can help you identify fish diseases and infections: “Manual of Fish Health” by Andrews, Exell and Carrington is a good example. Keep notes each day about what is happening with your quarantine tank and the inhabitants. This will help you to remember your experiences and assist you in the future.

Four factors in successful quarantine

  1. Sufficient quarantine length
  2. Monitoring the water parameters closely
  3. Carefully observing the animals each day
  4. Keeping accurate notes



When fish are sick administering treatment without delay can mean the difference between success and failure. There are a few medications that should be kept on hand for some of the more common infections. Keep a good copper-based medication such as Cupramine™, some praziquantel, formalin, and at least one good antibiotic handy. Maracyn-Two™ (minocycline), nitrofurazone, Furanase™ (nifurpirinol), kanamycin and neomycin are some good choices for antibiotics. Do not overstock with medications as they may expire before you use them.


Catching the Fish

Netting and removing fish from the water causes stress and frequently leads to injuries. This can be avoided by herding the fish into clear plastic bags or specimen containers with a net. Then the fish can be lifted from the aquarium in water. Clear plastic bags and specimen containers are more difficult for fish to see in the water than nets. This should make it easier to catch them and minimize the stress of chasing them around the aquarium.


Spare Equipment

You never know when you may be faced with a power outage or equipment failure. It may not happen when it is a convenient time for you to run to a store and purchase what you need. Stock an extra water pump, a heater, some airstones, batteries and at least one battery operated airpump for just such an occasion. Make sure that you have some firewood around for your fireplace in case you need to keep the house and the aquarium warm. It is also a good idea to make arrangements with someone that can take care of your aquarium in an emergency, or when you are away on vacation.


Research the Animals Prior to Purchase

Research may be the most important tool an aquarist can use. Knowing the needs, requirements and compatibility of each species prior to purchase will help you avoid making mistakes and greatly improves the animal’s chance of living a long healthy life in your care. You may learn that a species that you were considering has special dietary needs, requires a larger tank or simply is not compatible with another fish or invertebrate in your aquarium.


Selecting a Specimen

Once you have thoroughly researched a particular species of fish it is time to closely scrutinize each potential acquisition. Starting with a healthy specimen to begin with greatly increases their odds of long-term survival. Look for signals that indicate good health: such as eating, vibrant colors, a rounded appearance, clear eyes, fully extended fins, swimming normally and showing interest in the environment around them. Always ask to see the fish eat before you purchase it. Buying any fish that is eating less than two types of food is a risky proposition. If the specimen you are interested in is not eating then go back to the dealer in a day or two for another try.

Avoid specimens that exhibit labored or rapid respiration, are lethargic, have injuries, torn fins, are emaciated, or are obviously diseased. It is not uncommon for recently transported fish to be a bit thin in the stomach area. They will usually recover from this once they begin eating again, provided they receive an adequate diet. Fish suffering from long term or severe starvation will be thin behind the head and above the lateral line. These specimens may not recover.


Bringing them Home

Check the pH and water temperature in the tank of the specimen that you are interested in at the store. Then prepare your quarantine tank before you bring them home by matching those parameters as closely as possible (provided those parameters are safe).

Take a few precautions when transporting newly acquired specimens to reduce the risk of injury and stress on the animals. Start with enough water. A half gallon of water per three inches of fish is a good guideline. The rest of the transport bag should be filled with oxygen. Double bag the fish as leak insurance and to help insulate the water from temperature fluctuations. Keep the fish in the dark during transport to decrease their awareness of their surroundings and help reduce stress. Then get the fish into the quarantine tank as quickly as possible.



Any discussion of prevention and health in fish should include the topic of stress. Stress causes a myriad of physical, chemical and behavioral changes in fish. Stress can interfere with eating behaviors and digestion, cause difficulty in maintaining normal homeostasis (such as osmotic balance) and reduce immune function among other things. Behavioral changes are often the first indicators that some sort of stress is ongoing. Be aware of any potential sources of stress and immediately eliminate or reduce them whenever possible.

Stress factors can be classified into four loosely fitting categories: human interference, water pollution, animal interactions and extreme changes in the physical environment. Many of the stress factors mentioned below belong in more than one of these categories. Some examples of stress caused by human interference are: handling, toxins, photo shock, transport, electrical shock, crowding, malnutrition, noise or vibrations and netting or removing the fish from water. Water pollution would include: high ammonia, nitrite, or nitrate levels, heavy metals, high organic or suspended solids levels and other chemical toxins. Stressors that fall into the animal interactions category are: aggression, pathogens such as parasites and injury, hunger or nutritional problems related to aggressive behaviors. Stressors that fit into the extreme changes in the physical environment include: high carbon dioxide, low oxygen, improper hardness, turbidity, gas super-saturation, sudden changes in temperature or salinity, excessive water velocity, photo shock and low pH.


Next Installment

Part two of this two-part series will continue with an updated method for acclimation, ideas for providing a nutritious diet, and other tips for avoiding pitfalls so you can keep your stock in the best possible health.



  1. Wedemeyer, G.A. “Handling and Transportation of Salmonids,” Principals of Salmonid Aquaculture. Pennel, W. & Barton, B., eds., Elsevier Publishing, Netherlands, 1996.