Mysterious fish deaths explained

"My Fish Are Dying, And I Don't Know Why!"
by 2many fish - June 2002

What a common complaint this seems to be, and it's not always limited to newcomers to fishkeeping. Your lovely tank's inhabitants suddenly start to keel over, and for no apparent reason. Well, there is always a reason. Let's talk about a few possible causes.

1. New Tank Syndrome. How long has this tank been set up? If the answer is "less than 2 months," there is always the possibility that the tank is not yet biologically stable. In an established aquarium, beneficial bacteria have established themselves in sufficient quantities to be able to convert waste byproducts (ammonia) into substances less toxic. This is a common risk factor for any tank that has been set up for less than 3 or 4 months. To establish if this might be the cause of your fish losses, test the water for ammonia and nitrites. Test kits are manufactured by several leading companies such as Aquarium Pharmaceuticals, Sera, Tetra, etc. No aquarist should be without test kits for ammonia and nitrites. Any readings at all (anything other than zero) are dangerous to the health of your fish. If your readings are anything above zero, it's time to take aggressive action. First, a large water change (50% at least) is always appropriate, and will cut the toxic substances in half. If you do two changes in one day (one in the morning and one in the afternoon) of 50% each, the toxic substances will be cut by 75%. Then, continue to monitor and test for ammonia and nitrites every day until they read zero. If they do not read zero, continue with daily water changes of 50%. This will greatly reduce the risk to your fish, and will help with their survival. There are also substances (such as Amquel) that will convert ammonia into non-toxic substances that are still available to the bacteria, but which are non-toxic to fish. For nitrites, water changes are best. If you are keeping livebearers or goldfish, you can also reduce nitrite toxicity by adding aquarium salt at the rate of 1 tablespoon per 5 gallons of water.

2. Disease. Inspect the lost fish carefully. Do you see any evidence of diseases? Blood in the fins or under the scales is usually a sign of ammonia poisoning, but it can also be a bacterial infection. Do you see any signs of something on the fish that is three-dimensional? White spots, perhaps, or "threads" hanging from the fish? These can be parasites such as Ich or Anchor Worms. Do you see tufts of white cottony material on the fish's skin, gills or mouth? This could be fungus. Fungus infections can become so bad that they block the fish's mouth, preventing him from eating. Death follows soon after. Again, your first intervention should be several large water changes. This reduces the number of free-swimming parasites, and freshens up the water, which might have been the original cause of the fish falling prey to disease. Treat the symptoms appropriately. For parasites, my favorite treatment is Coppersafe. There are others. For fungal infectiions, you might consider using Acriflavine or Mardel's Maroxy.

3. Temperature. All fish have a preferred range of temperatures. Some prefer warmer temperatures, while others prefer cooler temperatures. Research your fish's requirements, and provide them with the proper temperature. In general, Goldfish prefer cooler temperatures (water in the 60's), while some fish such as Bettas and Angelfish prefer much warmer temperatures (81 degrees Farenheit or warmer). Warm water fish kept in cooler temperatures will always be under stress, and will become much more susceptible to diseases.

4. Toxic chemicals. Have you recently sprayed your kitchen or bathroom for roaches or ants? Has an exterminator recently treated your house for spiders? All insecticides are dangerous to fish to some degree or another, and it often does not take very much of the substance to kill fish. If you plan to spray your house or kitchen for any kind of insects, it is wise to first seal the top of the aquarium with plastic, and turn off any air pumps. Failing this, cover the aquarium with a large blanket. Allow at least 3 or 4 hours for the toxic fumes to subside before removing the cover from the aquarium. If your filter permits, running some fresh activated carbon in your filter box for a few days will greatly reduce the risk to fish.

5. Unexpected toxins. Before your fish began to die, did you dip your fingers or hands in your aquarium? Did you wash your hands thoroughly with plain castile soap before putting your hands in the aquarium? If you are a woman, do you use scented lotions on your hands, or do you spray colognes on your wrists? If you are a man, did you shave this morning, and if so, did you use a scented aftershave by splashing it on your face with your hands? These scented substances can be exceptionally toxic to fish, and can kill fish quickly. Before you dip your hands in your aquarium for any reason, first thoroughly wash your hands and arms with a plain unscented soap containing no antibacterial substances. Rinse your hands thoroughly, and then perform your aquarium maintenance. After working on your aquarium, wash your hands and arms again, only this time do use an antibacterial soap or detergent. Rinse thoroughly, to prevent infecting yourself with anything in the tank.

6. "Poison" rocks and ornaments. Have you recently added any rocks or ornaments not purchased at a trusted fish store? Calcitic rocks (containing large deposits of calcium or other harmful minerals) can cause unexpected changes in water chemistry. Be sure to test all rocks before adding them to an aquarium. Do not use sea shells or that interesting colored rock that you found on the beach last summer. Use only aquarium-safe decorations purchased specifically for the purpose from a reliable aquarium store. Rinse anything to be added to the aquarium thoroughly, scalding with hot water and then rinsing in cooler water. This will prevent the introduction of harmful and unexpected substances to your aquarium.

7. Diseased fish. Have you added any new fish to your aquarium in the past few weeks? Did you quarantine the new arrivals for several weeks before adding them to your aquarium? New fish can carry diseases or parasites, and infect all the other fish in your aquarium. Just because you've added new fish in the past with no harmful consequences does not necessarily mean that you can do it again. Always quarantine new arrivals, inspecting them carefully for any signs of diseases. Weight loss in the new arrivals is always a bad sign. Any unexpected fading of color, or patches of fading color on a new fish should ring alarm bells. If you are in any doubt about the health of a new fish, do not add it to your aquarium. Keep it in a quarantine tank until you are certain it is healthy.

8. Unexpected chemicals in your water. Municipal water departments occasionally add chemicals to kill algae or to prevent scaling inside the distribution lines. They usually do this on a regular schedule. Call your water department and find out what day of the month they add any extra chemicals. For example, they may make this a regular practice on the 5th of the month. Then, avoid water changes for 5 days after the addition of these chemicals, to prevent their introduction to your aquarium.

9. Extra chlorine. During the summer, bacteria in drinking water can become a serious threat. The United States is rarely affected by water-born diseases because water treatment plants aggressively treat municipal water with chlorine or chloramine. If you can smell chlorine in your tap water, that means the chlorine levels are very high. During summer months when they are adding extra chlorine, you may want to double the dosage of your dechlorinator. Simple dechlorinators (Yamato's No-Chlor, Wardley's Chlor-Out) cannot be overdosed. Even if you used ten times more dechlorinator, no harm would come to fish or other inhabitants of the aquarium. Don't be afraid to double-dose on dechlorinator during the summer. It will prevent your fish from being damaged or killed by chlorine.

10. Unstable temperatures. Do you regularly make a habit of checking your tank's temperature? This should become so ingrained in you that you automatically do it at every feeding. If you notice large fluctuations in water temperature, it could be that your heater is nearing the end of its lifespan. Tropical fish can easily tolerate temperatures up to 90*F, so it is best to set your aquarium heater for the desired temperature, year around. Let's say that you are keeping Angelfish, and you wish to keep a minimum temperature of 81*F. Set your heater to maintain this temperature. If the temperature rises with summer temperatures, your fish will not be harmed. But if the air conditioner should happen to chill the house down one evening, your fish will not be harmed because the aquarium heater will maintain the water temperature at 81*F minimum, and it will not drop below this temperature.

11. Spoiled food. Fish food has a finite life. After a period of time, fish food can become contaminated with molds and bacteria. It is best to maintain your food in as fresh condition as you can. Once you open it, mark the container with the open date. Try to use up the food before 60 days have passed. If there is still food in the container after 60 days, it may be good, but it may also be contaminated. If there is any doubt whatsoever in your mind, discard the container and use fresh food. If you buy containers of fish food in smaller sizes sufficient so that it will be used up within 60 days, you will find that it is easy to keep your food fresher. Unopened boxes or cans of fish food can be stored in the refrigerator or freezer. In the freezer, all deterioration of quality is virtually suspended, which means that you can keep several smaller boxes of food in the freezer and always have fresh food available when needed.

12. Environmental factors: Be careful not to install your aquarium where it is susceptible to being jostled or disturbed. Aggressively teach everyone that comes near the aquarium to refrain from tapping on the glass, or shaking the aquarium to see the fish jump and skitter around the tank. If there is ANY possibility that people might drop anything in the aquarium, educate them. Children should be taught that while they might like chocolate sauce on their ice cream, the fish really don't need any chocolate sauce added to their aquarium. If you have a toddler who is prone to dumping in unexpected chemicals such as household cleansers or bathroom products, place the aquarium on a stand where it is too high for the child to reach up and dump something in the tank. A heavy lid may be appropriate. Petco sells large, heavy wooden hoods that provide some protection for aquariums.

13. Overfeeding. I've saved the number one cause of fish deaths for last, because it is such an important topic. To emphasize this point, I'll repeat it once more: the number one cause of fish deaths in home aquariums is overfeeding. Fishkeepers want to be kind to their finned friends, and often succumb to the begging act of fish. All fish should receive Academy Awards for their performances in "I'm Starving, And No One Will Feed Me!" You can feed fish, and 10 minutes later they will behave as if they haven't eaten in a week. Do not succumb to this deception. Mature fish do not require more than a few mouths full of food per day. If you feed the fish once a day, and feed no more than they can consume in 1 minute, then they are getting plenty to eat. Do not confuse the fish owner's desire for an afternoon snack as meaning that the fish need one, too. Choose a time of day, feed the fish, and then put the food away until tomorrow. Be sure to teach other household members to refrain from feeding extra portions. Do not kill your fish with kindness. To overfeed merely risks the lives of your fish, and is doing them no favors.

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"My Fish Are Dying, And I Don't Know Why!" by 2many fish - June 2002

"My Fish Are Dying, And I Don't Know Why!"
by 2many fish - June 2002