Once you've decided that you want an aquarium the first step is deciding what size and where to place it. The general rule of thumb is, larger aquariums are less maintenance.
Think of an oil spill in a lake compared to an ocean, the same size spill will do more damage in the lake versus the ocean as the larger volume of water in an ocean will dilute the spill more. The same idea works in aquariums, a larger volume of water will absorb the ammonia created by fish waste and overfeeding etc. than a smaller volume of water.
Larger aquariums maintain water quality better as well because temperature, pH etc. will not fluctuate as easily in a larger aquarium. Not to mention that the larger the aquarium, the more fish you can have and the more dramatic a display you can create!
Placement of the aquarium is very important, you want to stay away from places like major traffic areas as fish can spook easily and may become stressed if there is a lot of movement surrounding the aquarium. Near windows or in rooms where a lot of direct sunlight may reach the aquarium will cause excessive algae growth and your beautiful aquarium display may soon become a green swampy mess! Make sure your aquarium is located near an electrical outlet as obviously you'll need to plug in a variety of electrical equipment such as pumps, filters, heaters and lights. Also, try not to place your aquarium in a spot that may be susceptible to drafts like right inside the front doors of an office etc. as this could cause temperature fluctuations that may result in disease for your fish.
Now that you've selected the size and the location for your aquarium than you have to (if, of course you're not hiring Aquariums by Design) set up the aquarium! The main thing you want to remember here is to make sure the aquarium is level and on a proper aquarium stand. Aquariums can leak or even crack if not set up properly!
Now that the aquarium is set up and the filtration is up and running along with the heater and air pump it's basically a waiting game, for at least 2 or 3 days anyway. The aquarium should be left running to allow everything to settle, the tank temperature to reach the desired level of between 77 to 82 degrees for tropical fish and to give it a few days to make sure the filtration is working properly. After the tank is filled you want to be sure and add the right amount of water conditioner for your size of aquarium so that the chlorine and chloramines are neutralized. I would suggest leaving the lights off during this break in period to avoid any unwanted growth of algae.
Now for the fun part, adding the fish! Lets assume the aquarium in question is a 90 gallon and we're adding an assortment of Tropical Fish. An aquarium this size is capable of holding between 15 to 25 fish or more depending on the size of the fish. The general rule of thumb is 1" of fish for every gallon of water, keeping in mind the maximum size of the fish and that a 90 gallon aquarium will really only hold roughly 75 to 80 gallons of water once you've factored in gravel and decorative displacement.
You never want to add the full amount an aquarium can hold all at once though. The Nitrogen Cycle is really the Life Cycle of the aquarium, simply put, fish give off waste in the form of ammonia that is very toxic. Nitrosomonas Bacteria convert ammonia into Nitrites which is toxic as well, then Nitrobacter Bacteria convert Nitrites into Nitrates which is far less harmful and is removed by live plants and water changes. The problem is there are no beneficial bacteria present in the aquarium when first set up so you have to start off slowly. In a 90 gallon aquarium adding 8 to 10 small hardy tropicals is recommended such as 5 Tiger Barbs, 3 Gold Gouramis and 2 small Green Severums. After a week or so with the initial 10 fish then more can be added each week until the maximum amount is reached. Plecostamous and other algae eating or cleaner type fish should always be added last as they usually do not eat anything but algae and can starve in newly set up aquariums as usually it takes 3 to 5 weeks before algae starts to appear. Adding the fish slowly will allow for the beneficial bacteria to grow and reproduce without suffering from a large ammonia spike. Usually after 4 weeks or so the beneficial bacteria has established itself within the gravel bed and on the inserts in the aquariums filtration.
Still keeping in mind that the aquarium is a 90 gallon tropical system fully stocked with 8-Tiger Barbs, 3-Gold Gouramis , 2-Green Severums, 5-Black Tetras, 3-Small Tinfoil Barbs, 5-Giant Danios and 2-Med. Siamese Algae Eaters the following maintenance is recommended. Bi-weekly water changes of 15 to 20% are recommended with every other water change being a gravel wash using a gravel tube syphoning device available at any aquarium store. The gravel vacuum will allow you to clean the excess debris out of the gravel bed without having to remove all of the substrate. It is much less stress on the system to do frequent smaller water changes than to wait a long period of time and do a large 50% or bigger water change. By doing more frequent smaller water changes the water perimeters like pH, alkalinity, temperature etc. will remain more stable and this will cause less stress on the fish. Cleaning the filter once a month is best even though some companies suggest their filters can go several months before cleaning or changing of media is necessary. Wether you're using a hang on type filter or a canister type it is always a good idea to only clean or change a portion of the media at a time and washing the remainder out in aquarium water not tap water. Beneficial bacteria grows in high oxygen levels so filter inserts where there is high water flow is the main place where this bacteria will reproduce and you never want to wash away too much of this bacteria all at once as this could result in an ammonia bloom and possibly fish loss.
Washing the portion that is not changed in aquarium water will allow you to clean off the larger pieces of debris and fish waste without killing off too much of the bacteria on the insert or filter media. If you were to use tap water to wash off these inserts than the chlorine in the tap water would kill off the bacteria. So basically every two weeks wipe the algae off the glass, clean any decorations that may be covered in algae, gravel wash 15 to 20% one week and then do a 15 to 20% water change only two weeks later. Clean the filter once a month and your aquarium should remain healthy and beautiful.
A few tips for keeping your aquarium cleaner and problem free along with regular maintenance are first and foremost DO NOT OVER FEED! Overfeeding is a very common problem, everyone seems to think that because they walk by the aquarium and the fish all seem to go crazy that they must be starving. The truth is, that the fish have learned that normally when there are shadows or movement near the aquarium it usually results in food being dropped in so basically they have YOU trained to drop in food when you see them swimming frantically at the surface. A fishes stomach is roughly the size of their eye so they really don't require very much food. It is always best to feed two smaller feedings per day rather than one large feeding, keeping in mind that most fish graze for food throughout the day. In the wild they eat small amounts frequently rather than eating large amounts of food all at once. A small pinch of food twice a day is best and if you notice that the food is sinking to the bottom of the tank without being eaten than your feeding too much. Overfeeding will result in higher ammonia levels, higher phosphates which algae feeds on to grow so in turn overfeeding could result in a lot more unwanted algae growth.
Keeping the aquarium light on for 8 to 10 hours maximum will help to keep the algae growth to a minimum as well. The more light the more algae, it's that simple! Usually the fish get enough light during the day from whatever light is coming in through the windows and because most people are at work and the kids are at school throughout the day. I would recommend putting a timer on the lights and have them come on in the afternoon and then go off in the late evening say from 1pm to 9pm. This way you can enjoy the aquarium when your actually home to view the aquarium and with a timer you'll never forget to turn the lights on or off. Don't overstock your aquarium! This is another common problem. People tend to want to fill their aquariums with way too much fish that will only result in higher ammonia and nitrite levels and disease. It's always better to have fewer healthier fish than a whole bunch of diseased sickly looking fish that will eventually start dieing off. Always make sure your aquarium has lots of water movement especially if it is saltwater. Water flow is important for the fishes fin development and growth and good water movement will help oxygenate the water causing good gas exchange at the surface. Power heads or an air pump with an airstone buried in the gravel are good ways to increase water movement with the airstone method being the most visually appealing.
Hopefully this will help anyone who wants to start their first aquarium and keep in mind that by following a few simple guide lines you can have a beautiful eye catching aquarium that will become a conversation piece for all your guests so go ahead, dive right in!