The nitrogen cycle is the most important principle that you need to understand concerning an aquarium environment. In nature, the fish enjoy what is called an "open" type system due to the very large water volume to fish ratio that they live in. This allows their water to be constantly renewed. In your aquarium, however, a "closed" type system exists where, without action on your part such as changing the water, their water will never be renewed and needs to be filtered properly for them to remain healthy. Proper filtering consists of 3 types, mechanical, chemical, and biological. The most essential of the 3 is the biological filtering that is accomplished by the nitrogen cycle, and is described below.
The cycle begins when you add fish to the aquarium. Between excess uneaten decayed food and waste that is generated by these fish, toxic ammonia is formed. (At pH levels of 7.0 and above, ammonia irritates the gill tissues of fish, and even at moderate levels, can cause death. At pH levels below 7.0, ammonia is present in the form of ammonium, and is much less toxic.) These ammonia levels will increase for about 2 weeks until aerobic bacteria called "nitrosomonas" grow to sufficient quantities in the filter to convert the ammonia to toxic nitrite. (Nitrite destroys the hemoglobin in the fish's blood and eventually prevents the blood from carrying oxygen) As this happens, the ammonia levels will quickly begin to drop as the nitrite levels slowly increase. These nitrite levels will continue to increase for about 2 weeks until aerobic bacteria called "nitrobacters" grow to sufficient quantities in the filter to convert the nitrite to much less toxic nitrate. Again, as the nitrite levels quickly decrease, the nitrate levels will slowly increase. Once your tank has reached this point (about 5-6 week's total), it is said to have "cycled".
Nitrate is harmless except in higher levels (such as above 40 parts per million) which will promote algae growth in the tank. Even higher levels can result in stress that can weaken the immune system of the fish and make them susceptible to disease. All you need to do now, is to perform your regular partial water changes in order to keep a moderately low nitrate level. If this practice is followed routinely, you should have no problems maintaining your biological filter.
So, you think you might want to try tropical fish as a hobby. You've always admired those fascinating fish and beautiful aquariums at other peoples' houses, and considered giving it a try yourself, but you don't know anything about taking care of fish, and have always heard that there is a lot of work involved with maintaining an aquarium. Well, as far as the amount of work involved, you can expect to spend about 30 minutes every 2 weeks keeping your aquarium clean. If this sounds like too much time to spend, you might want to try another hobby. Remember, it's really only work if you don't enjoy what you are doing. I actually consider the maintenance as fun! And when you finish, there is that rewarding feeling that you have improved the environment for your beloved pets.
Well, are you are still interested? If you are, there are 3 questions you need to answer before we get started:
1) What type of fish should I keep?
2) How much physical room do I have?
3) How much money am I able to spend?
The first question is difficult especially for a beginner, since you are not aware of what types of fish are available. Generally, freshwater fish will fall into 3 basic categories. The most commonly kept fish are the community type fish, which live and play well with others. The next category would be the aggressive type fish, usually from the cichlid family of fish, and need to be kept alone or with other cichlids of similar size. These fish will almost certainly eat smaller and more timid fish. The third type actually falls somewhere between freshwater and saltwater fish called brackish water fish. These fish need salt added to their water in order to survive. As a beginner, you should first visit your local pet shop and look at the different types of fish available and decide which type you would like the most. I would recommend, at least for your first tank, that you go with the community type fish. There is usually more of a variety available and they are "generally" less expensive should you have a few expire on you while you are still learning.
The second and third questions are sort of related. I strongly recommend that you purchase the largest tank that you have room for, and can afford. No, I'm not a tank salesman! Good stable water chemistry, which is the most important factor in the survival of your fish, is much easier to maintain in larger tanks. In fact, I would not recommend a tank smaller than 20 gallons. I can hear what you are thinking from here! "Maybe I'll just buy a small tank and see if I like the hobby." Believe me, if you do that, you won't. You will experience water quality that will suddenly swing from one range to another as you fight to get it stabilized. You will then start to lose one fish after the other until you finally give up and put that little tank in the back of the closet or down the basement never to be seen again. Please understand, this is not because you aren't "good enough" to take care of fish. Even experienced aquarist have to be very careful with small tanks. If you want to give yourself a fair chance to get started, please try to stay away from the small tanks.
Now that you know what size tank you want, you need to consider everything else that may or may not be required to establish your new aquarium.
Filter: Required. I won't go into all the details about all the different types of filters here. That's a subject for a separate article all by itself. There are many different types of filters such as, power, undergravel, sponge, canister, fluidized bed, and biowheel filters. These filters provide you aquarium with mechanical, chemical, and biological filtering, but not always all three. As a minimum, your filter must provide biological filtration for your fish to survive. As far as the size of filter required, your tank water should be cycled through the filter 4-5 times per hour (ie. 30 gallon tank needs a filtration rate of about 150 gallons per hour).
Heater: Required. You should use 2 heaters with a rating of 2.5 watts per gallon placed at opposite ends of your aquarium (ie. 30 gallon tank would need 2, 75 watt heaters). The reason that I recommend 2 heaters rather than one is because even the best one's have been known to fail. And when they fail, they almost always stick in the "on" position. By using 2 heaters you won't accidentally cook your fish if your heater fails, and if they are working you will have uniformly even heat distribution on both sides of the aquarium. You should also purchase a small aquarium thermometer to monitor your water temperature. Even if the heater(s) has some type of temperature gauge, don't trust it, they are usually not very accurate. If you have a 55 gallon tank or larger, you should have a thermometer at each end.
Lighted Hood: Required. Generally when you purchase a new tank, you will also get the lighted hood as a package deal. If not, you need to purchase one for your tank. They provide 3 important services. First, you will need a light at night time to see all your wonderful fish. Secondly, the hood serves as a lid for the aquarium to prevent accidental fish suicides. Many fish tend to jump with an open surface, and without the hood, you might find some of your fish on the floor. Lastly, the hood slows down water evaporation from the tank.
Tank Stand: Required. As with the lighted hood, many times the stand will be included with your packaged tank purchase. If not, you can use anything you like as a stand, just be very sure it can support the weight! Check out the article on this page titled, "Conversions, Calculations, & Data", in order to determine the total weight of your aquarium.
Fish Net: Required. You need a way to move fish in and out of your tank.
Test Kits: Required. As a minimum I would recommend kits to measure pH, Ammonia, Nitrite, and Nitrate. The pH kit will be needed every few days to ensure your pH remains stable, and the other kits will be required mainly during the initial cycling of your tank.
Food: Required. Pick up some staple flake food. This will be sufficient for now.
Water Siphon: Required. Some people will say that this is not a necessity, but I disagree. You need some type of siphon in order to vacuum the gravel and perform partial water changes.
Gravel: Although not absolutely required (unless you are using an undergravel filter of course) but highly recommended. Gravel provides a very attractive floor bed for your aquarium and a suitable substrate as a means for securing plants and ornaments to the bottom of the tank. You will need about 1 pound of gravel for each gallon of tank size (ie. 30 gallon tank would require 30 pounds of gravel). Since most gravel in pet stores is pre-packaged in 5 pound bags, you would need 6 bags for a 30 gallon tank. Also, no matter what it says on the gravel bag, always rinse the gravel thoroughly before adding to the tank.
Rocks, Plants, Wood, Ornaments: Not required but they do improve the visual aspect of the tank. You will need to decide if you want to go with plastic, silk or real plants. The plastic plants require no care and will last forever. Real plants require maintenance, but look very nice and remove nitrates from the tank. As far as rocks and wood, be sure they are aquarium safe before using. Picking up rocks and wood from your yard could introduce a lot of unwanted inhabitants and contaminants to your tank. Ornaments are up to you.
Fish: Absolutely, positively, for no reason, should you add fish to your tank on set-up day!!! For reasons that are discussed later in this article, you need to be patient while populating your new aquarium.
Ok, now it's time to get the tank started. Before putting anything into the tank, you should fill the tank at least one third full and check for leaks. If it does, it's much easier to fix the problem while the tank is empty. If it doesn't leak, drain the water and clean the tank using warm water and a rag. No soap or detergents! Even the smallest amount of residual detergent may kill your fish.
You can now attach/install your filter, heater(s), gravel, and decorations. To begin filling the tank, I would recommend placing a large bowl on the gravel in the center of the tank. When you begin adding water, pour it into the bowl and allow the overflow to slowly add the water into the tank. Pouring water directly into an empty tank will create a mess with your gravel. Once the tank water gets a little higher you can remove the bowl and add the water directly. When the tank is full, start the filter and set your heater(s) for 75-77 degrees Fahrenheit. You will need to check your thermometer(s) periodically over the next couple of days, and adjust your heater(s) to obtain the proper temperature.
Now, sit back for the next 48 hours and take a break. This will allow for all the air bubbles on the glass to disappear and the chlorine and other gasses in the water to dissipate. After this waiting period, test the pH of your water and adjust for a pH of around 6.8. For the first 4 weeks, try to maintain a level between 6.7 to 6.9. After this period, anything from 6.8 to 7.2 is just fine for a community aquarium as long as it is consistent. Do not continually keep changing the pH of the water to make it "more correct", this will do much more harm than good. The reason for keeping the pH below 7.0 in the beginning, is due to the fact that ammonia that will initially be present in your tank, takes the form of ammonium at pH levels below 7.0. Ammonium is much less toxic to the fish than ammonia.
Finally, now you can add fish to your tank! Go down to our pet store and pick out 2 or 3 (NO MORE) hardy inexpensive fish. I would recommend a couple of catfish. They are very hardy fish and you will need about 1 per 10 gallons of tank water eventually to perform bottom cleaning maintenance. When you get home, do not just dump the bag of fish and water into your aquarium. Never, ever, add the water from another tank into your aquarium. You could be adding millions of unwanted micro-organisms into your tank. You should float this bag of fish in your tank for about 1 hour. Every 15 minutes, add a small amount of water from your tank to the bag, re-close the bag, and continue floating. This process is acclimating the fish to both the temperature and pH of your tank water. After the 1 hour period, carefully pour your fish from the bag into a fish net, and then add the fish to your tank. Do this as gently as possible since netting fish is usually very stressful to them.
Note, your crystal clear water may now become cloudy. This is normal, don't worry it's usually due to a bacteria bloom and will clear itself in time. Until your tank has cycled, usually about 6 weeks, your tank can experience these blooms due to the fact that your filter cannot yet handle all the bacteria and it will free float in your tank. This is why you should only add a couple of fish at first. If you add too many fish at once, you will overwhelm your filter, which is commonly called "new tank syndrome". Most people cannot wait to fill their tank with fish in the beginning, and end up with lot's of dead fish soon after. You can help your filter and accelerate the cycle time by borrowing some gravel from a friend's already cycled tank and placing it in your filter box. You can also try some of the commercially available bacteria culture additives, although they have never seemed to work for me.
Now that you have fish in the tank you will obviously need to feed them. Be very careful, it is all too easy to overfeed fish. They do not require very much food. I would recommend you feed them 3 times a day and only enough food that they will consume in about 5 minutes. More than that, and you are just polluting your tank.
You should now wait at least two weeks before adding a couple more fish to the tank. The biological load on the filter should be increased gradually, even after the tank has cycled, since the bacteria colonies in the filter will only develop sufficient numbers to handle the current load present in the tank. Too many fish added at once, and hello cloudy tank again until more bacteria can establish itself in the filter.
Be sure not to overcrowd your tank. This stresses the fish and may be more than your filter can ever handle. As a general rule of thumb, you can add about 1 inch of fish for each gallon of tank water (ie. 30 gallon tank = 30 inches of fish). Much more than this, and you may be overcrowding the fish.
Lastly, I would like to talk about partial water changes. This is where you should vacuum the gravel and remove about 25 percent of the tank water. This should be performed about every 2 weeks. Some people do not believe in changing their "aged" water, but it is necessary for several important reasons. It removes nitrates and prevents potentially dangerous buildups, it retards algae growth, it replaces trace elements in your water, it keeps your tank water composition similar to your tap water so that you do not shock the fish when you do replace the water, and it promotes better growth in your fish. Just remember to add a water conditioner that removes chlorine/chloramine whenever you add tap water to your tank. Also, do not forget about keeping the filter clean! This should be performed about once a month, and should be done very carefully. You should treat your filter like a living entity. Remember, there are "live" bacteria living in there. Lack of oxygen, water, or rinsing them with chlorine in the water, will destroy them and wipe out your biological filter. This means that you will need to establish bacteria in the filter all over again, except that you may now have a lot of fish in the tank! A very bad situation. The best solution is to rinse your filter with tank water that is removed during the partial water change so as not to damage your bacteria.
Well, that's about it for getting started. It may seem to be a lot to learn at first, but it will become routine in a short time. Hang in there, and enjoy your fish!
The chart below contains most of the more common freshwater fish that you will find at your local pet shop. I have divided the list into 3 categories of behavior, and defined as follows:
Community Fish : Unless marked with a note, these fish can be safely mixed together in the same aquarium.
Semi-Aggressive : These fish are usually peaceful when they are small, but can become fin nippers or chase the others around the tank when they get bigger. If you really want to put one of these fish in your community tank, you can, but keep an eye on them as they get bigger.
Aggressive Fish : Do not mix these fish with any other type fish except similar sized aggressive fish. They will bully and even eat smaller and more timid fish.
Category Community Semi-Aggressive Aggressive
Dwarf Gourami Honey Gourami Black Paradisefish
Flame Gourami Kissing Gourami
Siamese Fighting Fish/Betta(1)
Banjo Catfish Bumble Bee Catfish
Chinese Algae Eater
Upside Down Catfish
Black Neon Tetra Black Widow Red Belly Piranha
Black Phantom Tetra Bleeding Heart Tetra
Cardinal Tetra Buenos Aires Tetra
Congo Tetra Silver Dollar
Head & Tail Light Tetra
Rummy Nosed Tetra
Angelfish Firemouth Convict
Blue Acara Severum Green Terror
Discus (2) Jack Dempsey
Festivum Red Oscar
Cherry Barb Flying Fox
Bala (Tri-Color) Shark Green Tiger Barb
Black Shark Red Tailed Shark
Blue Danio Rosy Barb
Giant Danio Tiger Barb
White Cloud Tinfoil Barb
Guppy Swordtail Knife Livebearer
Australian Rainbowfish Archer Butterfly Fish
Boesmani Rainbowfish Freshwater Puffer
Bumble Bee Goby
(1) Only 1 male Siamese Fighting Fish/Betta per tank. 2 Males will fight to the death if they are in the same tank! You can have as many females in the tank as you wish.
(2) Discus should not be kept with other fish other than catfish, loaches, neons, or cardinal tetras. This is due to the fact that they are very susceptible to disease, they require a warmer water temperature (85 degrees F), and are sometimes slow eaters and will not fight for food.
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