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Care of the Freshwater Aquarium



     With proper care an aquarium takes only a few minutes of your time a day.  You should prepare your tank before any fish are purchased.  It is important to realize that the aquarium is an ecosystem like our planet.  The fish’s wastes must be biologically broken down to prevent the toxins from killing the fish itself.  The fish urinates ammonia, which is converted by bacteria into urea and nitrites.  The nitrites are then modified to less toxic nitrates.  It is a fairly complex process with a lot of different types of bacteria required.  These bacteria cannot be purchased and must naturally be introduced.  It is best to purchase one fish and then wait a 2-3 weeks before more are slowly added.  It may take 46 weeks for the nitrification bacteria to be established.  Adding too many fish at once will create a “new aquarium syndrome” where the ammonia and nitrites accumulate killing the fish.  Any time antibiotics are added to the water, the bacteria are killed.  Don’t use antibiotics unless directed by your veterinarian.  Thoroughly cleaning out the tank and boiling/sterilizing all the rocks and gravel will also kill the good bacteria.  These bacteria live on the rocks within the aquarium.  We recommend 1 to 3 inches of gravel in the bottom of a tank, or about 12 pounds per gallon. The 1/8 to 3/16 inch gravel is an adequate size.  A good pump, filter, and heater are necessities.

     The cleanliness of the fish water is of the same importance as the quality of air we breathe.  We recommend that you change 10% of the water each week.  By suctioning off the bottom with a siphon tube, visible wastes can also be removed.  More water can be removed if the fish are sick or if the bacterial balance of the tank has been disturbed.  Try not to remove more than 25% of the water during one day or you will need to dechlorinate the new water.  Always slowly add water in order to prevent a shock of the fish from temperature changes. (When you purchase fish, always leave the bag in the water for 30 minutes, then every 15 minutes add 1020% of the aquarium’s water to the bag for 34 times before releasing.  We recommend that you isolate all new fish for 2+ weeks, or one month if possible, before adding them to the aquarium.)   A few species of fish require an alkaline pH of the water, while some may require an acidic pH.  Some species require a hard water (with a lot of minerals), while others require a soft water environment.  With normal changing of the water most species are adequately cared for.  The varieties of tropical fish can come from all over the world, and each type is used to a different water quality.  Sometimes it is best to realize that some species should not be raised with others, and this knowledge can usually be obtained from an experienced person in a high quality fish store.  We recommend that you purchase your fish from a quality source, not a high volume store that can transmit diseases because of their multiple fish shipments and inexperienced staff.  If you should purchase a test kit, we recommend that you keep the pH at around 6.07.5; 6.8 is best.  The chlorine should be 0.003 ppm.  The ammonia level should be kept below 0.1 ppm; a higher level of 0.3 ppm is lethal.  If your water ever tests <5.5 ph, >9.0 pH, or >1 ppm free ammonia your management of the water and feeding practices need to be closely examined.  The nitrate levels are adequate at 35 ppm or less, with a water change required at 70 ppm.  Nitrite level should be less than 0.05 ppm, as 0.1 ppm is toxic.  The hardness of the water should be between 50150 ppm, preferably 50 ppm as calcium carbonate.  Oxygen should be about 5 ppm for tropical fish.  Again, by changing the water as directed, most of these toxic levels can be avoided, without the need for testing.  The new aquarium syndrome handout also discusses chlorination of water versus chloramine.  It is very important to siphon or dump your aquarium water and plants out onto your lawn and not down the public sewer.  Many noxious plants, parasites and exotic fish have been introduced into our waterways by this method of accidental contamination.

     Some algae is to be expected.  Green algae usually indicates too much light, while a brown algae may suggest that not enough light is provided each day.  Because live plants are very difficult to grow in most aquariums, we suggest that you use the plastic plants at first; then slowly experiment with the live plants if you want.  Some bottom feeding fish may uproot your plants, and the Cichlids are especially noted for being destructive towards uprooting plants.  Snails and other animals help keep the algae population down.  Changing the water, which removes the “fertilizer”, helps with controlling algae.  Chemicals that control the algae will usually harm the good bacteria and some of the live plants you may have in the aquarium.  Use fluorescent light bulbs designed for plants if you are trying to grow live plants.  We recommend 810 hours of light each day.  A rule of thumb is 3 watts of light per gallon of water (60 watts for a 20 gallon aquarium).  The water temperature will vary with the species, but usually an 78 degree temperature is adequate.  Some tropical species require a temperature as low as 72 degrees, while others may prefer 84 degrees with 78 as a medium range.  It is recommended to use a GFI outlet, or a Ground Fault Interrupter adaptor, wherever there is water and electricity.  A quality electrical store carries these adaptors and/or an electrician can install such an outlet.  Because goldfish require nonheated water, they should not be kept with the tropical fish.   We advise a cover on the aquarium to keep out other pets (cats) and possible poisons, such as insecticide sprays.

     It is very easy to unknowingly purchase some fish that are aggressive enough to literally kill other fish.  A quality pet store can direct you to purchasing the type of fish that would be compatible with the fish you already have.  We commonly see overcrowding as a problem in fish tanks.  You should take the width of your tank, multiply it by the length, and divide by 12.  This is the estimated maximum length of adult fish in inches desired for most species.  An inch of fish per one gallon of water is also a similar calculation of maximum density.  The newer designer tanks are tall and slim, which can cause bladder disease in some fish because of the extreme variation in pressure from the top of the tank to the bottom.  We do not recommend very many fish in the tall, slim tanks.  If you have Beta fish or goldfish, and no air pump, the surface area of the aquarium determines the amount of oxygen that gets into the water;  one inch of fish per 24 square inches of surface area for cold water fish.  We do realize that with some species, like guppies and Beta fish, you can have more crowded conditions, but this is not always advisable.  The temperature of the water is very important to the amount of oxygen available to cold water fish.  The colder water holds oxygen better than warm water which is why some species like trout cannot live in most aquariums inside the house.  Too many fish results in stress, and any excessive stress on an animal will result in diseases and parasites becoming more common.  Some species are solitary fish, such as beta fish, yet on the average we recommend at least 2 fish per tank.  Some fish need to be in groups and require that they live in a school of fish of the same species.  Breeding fish is as different as the species are, and we ask that you search out specific resources on each type.  Most all fish will naturally eat newly hatched babies, even if they are their own species.

     We all tend to overfeed ourselves and our pets, and fish are no exception.  We advise feeding your fish twice a day as directed on the fish food container.  Some foods are more concentrated than others, but usually it is only a small percentage of difference.  If fish are not eating all their food within 5-10 minutes, twice a day, they are usually being overfed.  Decaying food causes more problems than fish being underfed.  Look for a fish food that has 3036% protein, 10% fat with the omega  3 fatty acids/linolenic series, and the 10 essential amino acids.  Fish require 15 vitamins which deteriorate with time.  Do not leave the food uncovered, and discard the food after its expiration date.  If you are going on vacation we recommend a 7 or 14 day feeder to daily feed your fish while you are gone; these are inexpensive and under $30 (2014).  We do not recommend the decaying fish block that can feed your fish for a week; if you do use this method then remove the block when you come home, siphon up the excess on the bottom and change 10% of the water.

     There are a lot of “super medicines” that supposedly cure almost every disease that a fish can get.  Beware of these mixtures, in order to prevent an upset of the bacterial population in your main tank.  Should you be asked to use one of these products that kill bacteria you should change 10% of the water daily for 12 weeks, as if you have a new tank.  By killing off the disease, you may also kill all the bacteria that modify the fish’s wastes.  The disease called “ich” is the most common parasite.  It is a ciliatetype organism that causes the fish to have white spots or raw areas on their body.  The Ichthyophthirius parasites rarely lives in water above 80 degrees.  We advise formalin as one of the treatments.  Other causes of sick fish may require an examination or possible autopsy with lab tests.  Please ask for our biosecurity handout if you plan to add more fish to the existing aquarium.  We recommend that you and especially your children wash your hands after working with aquarium water.  Any water with exposure to animals or humans has a potential for bacteria such as Salmonella to be found within it.  

     With salt water aquariums the basic care is the same, except that the specific gravity of the salt water needs to be tested routinely.  Overfeeding is also a common problem.  We have books in our library that you may come in and read about fresh water and salt water aquariums.


The Staff at the Nelson Road Veterinary Clinic