I would offer a free brochure about this vital process in every pet shop or marketplace with every purchase of fish or aquariums.

The volume of water for the fish in nature is basically unlimited, so the waste products become diluted to very low concentrations that don’t harm them. Since the aquarium has a low volume of water compared to the natural environments, the waste produced by fish, excess food and dead plants quickly affect the quality of the water. Fortunately, the bacterial colonies convert these toxic substances into safe by-products. For newly setup aquariums, the water might be toxic for fish for a few days to weeks, before the bacterial biologic filter forms and is able to support the number of fish and waste produced. This is why it is always recommended to add only a few fish at a time, even after the cycle is completed, to allow the bacterial filter to adjust.

The Nitrogen Cycle – this is the process of converting the waste materials to safe by-products by the biologic filter. It starts in every aquarium, and it’s beginning is usually marked by a “milky” cloudy water for a few days. You must not add any new fish until the cycle is completed.

There are ways to start and complete the nitrogen cycle in your aquarium without fish, but I am sure you are looking forward to seeing fish in there, so we’ll discuss about the cycle WITH fish.

The Nitrogen cycle has 3 stages:

STAGE 1: Add only a few hardy fish to get this process started. A pair of corydoras and a pair of danio zebras would be just fine. The nitrogen cycle begins when live animals(fish, snails, etc) are introduced to the aquarium. The cycle requires live animals to go on to the next stages because the bacteria survive on these forms of waste described above. You don’t need to buy bacterial products to speed things up. Just wait for the cycle to complete, let the nature take its course. Some people suggest to “seed” the filter with bacteria from an older tank but opinions here vary – such bacteria exist everywhere so it’s enough to trigger the start of the cycle by adding a few fish and their waste products will help the bacteria multiply. The waste is converted into ammonia. The ammonia can be ionized (Ammonium = NH4) or unionized (Ammonia = NH3). Ammonia is very toxic to fish, so you want to have this down to 0. Ammonia rises in a few days after adding the fish, because of the waste they produce that is more than the biological filter is able to process. Feed the fish very light, once or twice a day (please remember, more food = more ammonia!).

STAGE 2: The Nitrosomonas bacteria eliminate the ammonia in a few days by converting it to nitrite (NO2) which is also toxic to fish.

STAGE 3: The Nitrobacter bacteria convert the nitrites into nitrates (NO3), which have a lower toxicity for fish if they are in moderate levels. Regular water changes keep these nitrates in safe ranges, but you might want to get nitrate tests to measure the levels from time to time, to make sure your fish are safe. Plants also use some of these nitrates, so a tank with many healthy plants is safer for the fish. Plants utilize nitrates as a fertilizer and everybody is happy!

The cycle is completed when nitrates are being produced (and ammonia and nitrite levels are zero). Usually this takes from 2 to 5 weeks, depending on the temperature (the higher it is, the faster the cycle ends).

REMEMBER: ammonia and nitrites should be 0 before you can add more fish. Most beginners don’t read about this extremely important cycle and keep adding fish while the ones they bought last week died “with no reason”. This is the “New Tank Syndrome”. Unfortunately, people kill thousands of fish before understanding this NATURAL cycle that can’t be avoided. Adding more fish before the cycle is done increase the ammonia levels so much that they are lethal, because the biological filter (bacteria) can’t process that amount. The same happens when you add too many fish even after a complete cycle, in a “mature” aquarium. So, it is recommended to add only a few fish from time to time.

If you already got a bunch of fish for your new aquarium, you can still fix the mistake and avoid fish death by buying ammonia neutralizing products.

STEP 1: BASIC INVENTORY BEFORE GETTING STARTED

MANDATORY: Make sure you have all these items before starting to setup your aquarium:

• aquarium (doooh!) : most if not all the beginners tend to get a small aquarium thinking that it is enough but let me tell you that the bigger it is, the better. There are a few reasons for getting a larger aquarium, one of them being the fact that you will always want to get more fish and plants, after you start to enjoy the hobby; a small aquarium isn’t suitable for fish and overcrowding fish is the first trigger for various diseases and even death. Another reason to get a bigger aquarium is that the large aquariums are more stable when we talk about water chemistry and temperature (they vary slower than in small aquariums – the slower they vary, the better for the fish and their health). Generally, don’t start with an aquarium smaller than 100 liters (remember that the gravel, filter, ornaments and the fact that the tank must not be filled 100% with water already reduce the volume of water available for your fish).
• aquarium filter: the filter must be chosen for the volume of your aquarium (check their ranges per volumes of water – don’t get stronger or weaker filters, just get the one that fits the volume of your aquarium). You can choose from external and internal filters. The advantage of external filters is that they don’t take up space inside your aquarium (and also helps with the beauty of your aquarium if you’ll want some aquascaping / aquarium design).
• aquarium gravel: there are many options here
• aquarium heater: usually a heater is necessary to keep the temperature of the water in the right range for the species of tropical fish you have. Don’t even think about getting a heater without a thermostat. On the other hand, I don’t use a heater right now since the temperature of the room always keep the one inside the aquarium at the right ranges for the fish I have. This saves some bills and also declutters the aquarium.
• light units: won’t get into detail here, just get the light equipment suitable for your aquairum. You might also want to get a plug timer to turn on and off the light every day.

OPTIONAL:

• ornaments: you might want to get a few ornaments to complement the plants and general look of your aquarium. The best are natural ones like rocks and different wooden roots (please make sure they are suitable for the aquarium – get them from a fish store not from your backyard!)
  PLEASE don’t get colored gravel (pink gravel?! OMG, no!), scuba divers, cranes, etc – they just ruin the little nature corner you want in your home by setting up an aquarium.
• aquarium plants: since you shouldn’t add live plants or fish right from the beginning, you should get these later, after your aquarium is ready to host life.

STEP 2: PLACING THE AQUARIUM IN YOUR HOME

You have to choose the location for your aquarium, and believe it or not, this is a difficult step. There are a few things you must know before deciding the final location of the aquarium in one of your rooms:

• The aquarium must not be visited directly by the sun light (if it does, there are big chances that your water will turn so green that you won’t be able to see the fish :)). This is a green algae invasion and it is very common for beginners.
• In case your aquarium didn’t come with a stand of its own included, you must be very careful in choosing the stand it will be placed on. This must be able to sustain the full weight of the aquarium (think about the sum weight of the empty aquarium, the gravel, the internal filter, volume of water). Don’t forget to make sure that the floor is also capable of sustaining all these.

STEP 3: INSTALLING THE GRAVEL AND ACCESSORIES
Wash the gravel thoroughly first. Use a big bucket filled with water and only fill 1/4 of it with gravel to clean it very well. Stir the gravel a lot and change the water several times until the water comes clean after stirring the gravel. Then you can add it to the tank. Place the filter in position reading the book of the aquarium and/or filter carefully. Add the heater if you are going to use it.

STEP 4: FILLING THE AQUARIUM WITH WATER
Before filling the tank with water, wash it a bit only using clean water, no soap or detergents! These can hurt your fish even if you think you washed them away properly. When you add the water, please don’t fill the aquarium 100%, keep a height of 3-4 fingers from the top empty. Some aquariums bought as a package also have a red line indicator and the water must be kept below that level. To avoid destroying the layout of your gravel and ornaments, place a clean piece of paper and then pour the water on it. You can remove the chlorine from the water using “AquaSafe” or any other brand, but why not save some money since you don’t bring the fish so quickly anyway?

STEP 5: CYCLING OF THE AQUARIUM
This is the process in which the live bacteria “filter” builds in the tank. It is very important to wait until it is established. If you don’t, your fish might die. Usually it takes several weeks to complete. However, you can complete this step with a few fish in your aquarium. LINK

STEP 6: ADDING THE FISH
This is the moment we’ve all been waiting for! :) You’re excited, but don’t hurry to add too many fish. It is recommended to add only a few fish every few days so that your biological filter adjust to the new population and waste produced. You can set a rule of adding a few fish (4-5) every weekend, for example. You are looking forward to seeing the fish swimming in your aquarium, but…you need a bit more patience here!

Let the bag with fish float in the tank for about 10 minutes (especially if it is winter) so that the temperature of the water in the bag equals the one in the tank. Then, to avoid the PH shock, open the bag and attach it to the border of the tank with a hook and add some water from the aquarium to the bag (about 20% of the bag). Do this again every 10-15 minutes for 5 times. Every time reduce the water volume of the bag by 20% to allow new water from the tank. Then, the fish are ready for their new home! Slowly let them escape from the bag in the aquarium.

They will need some hours or even days to get used to their new environment. Don’t feed them in the first hours, since they will avoid food anyway, being a bit shy at first. However, if you already have other fish, this process of getting used to the tank is much faster, the new fish being encouraged by the existing inhabitants.

How many fish to add? A general guideline is the “inch per gallon” rule.

DONE!

Now you have to write down a schedule of maintenance for your tank, with regular water changes once every 2 weeks or more often, depending on the number of fish you have. Regular water changes keep the fish healthy by removing bad chemicals and waste and they also stimulate plant growth.

After you reward yourself watching the new fish, get ready for the next article on aquarium maintenance.