If you're considering setting up a saltwater aquarium you have almost certainly heard that the tank needs to be conditioned or "cycled." So what is the conditioning process and what does it really mean? Conditioning is basically process of building up of beneficial bacteria that will colonize your gravel bed. These bacteria play an absolutely critical role in converting some of the highly toxic elements in your tank into fairly benign chemicals. In fact, this process is so critical that your animals cannot survive without it. This is known as the nitrogen cycle. You don't need to be a chemist to understand the process, but you do need to have a fairly solid basic understanding to give you're new aquarium a fighting chance. So let's have a quick review:
1. Animal waste products, leftover food and other organic materials in the aquarium decompose producing ammonia. This is extremely toxic to the animals in your tank and will quickly kill them if the level of ammonia in the tank rises too high.
2. Bacteria that converts the ammonia to another chemical called nitrite will begin to colonize in the gravel bed of your tank. Nitrite is also toxic, although less so than ammonia, but will also lead to the demise of your animals if not removed.
3. Now a second type of bacteria will also begin to colonize in the gravel bed and convert the nitrite to another chemical, nitrate. Nitrate, although not immediately toxic to most fish, is not well tolerated by some of the more delicate sea creatures such as corals and invertebrates. Nitrate will gradually accumulate in your tank and can only be effectively removed by regular water changes.
The bacteria that perform this process are not in the gravel that you bring home from the pet shop or in the saltwater mixture that you use when you setup your tank. It will take time for these bacteria to grow naturally and colonize within your gravel bed. This process is known as conditioning or cycling, and here's the basic process:
1. You add new (hardy) fish to your new setup. Over the next few days they will consume the food that you feed them and produce natural waste products which will break down naturally and produce ammonia as a by-product. During the first two weeks the ammonia level will rise and peak after about 12 - 14 days. Fish that are particularly delicate will not be able to tolerate the ammonia in the tank and will likely die, so make sure you use strong, hardy fish for this stage of conditioning. Damselfish are an excellent choice. The ammonia in the aquarium will trigger the growth of the first nitrifying bacteria. This nitrifying bacteria actually feeds on the ammonia and converts it to a somewhat less toxic chemical, nitrite.
2. As the nitrifying bacteria spread and colonize your substrate they continue consuming ammonia and releasing nitrites. During this part of the cycle, ammonia levels will begin to decrease and nitrites will steadily increase. These nitrites are also toxic and need to be removed. Luckily, a second type of bacteria, denitrifying bacteria, will feed on the nitrites and convert them to nitrates. The nitrite level in your aquarium will peak about 6 - 8 days after the ammonia level peaks, putting you into week three of the conditioning process.
3. The denitrifying bacteria continue to grow and colonize the substrate and feed on the toxic nitrites, converting them into fairly benign nitrates. At this point the nitrite levels should steadily decline and the nitrate level will slowly rise. Most aquarium fish are not particularly sensitive to nitrates, although many invertebrates and corals will not tolerate even moderate nitrate levels. The only way to effectively remove these nitrates is with regular water changes.
Once this cycle is complete the ammonia and nitrite levels should settle below 0.1 ppm (parts per million) and should now be safe for most marine life.
Simple test kits are available at your local pet shop that can measure the levels of ammonia, nitrite and nitrate in your water. Most of those same pet shops will also test a sample of your aquarium water for a small fee. Either way, check the levels at least once a week during the conditioning process and track the changes. This is the only way to be sure that your tank has properly cycled.
The entire conditioning process can take close to one month to complete. This is where most new aquarists make their biggest mistake. After spending a decent amount of money on their new system and investing the time to construct it, they grow impatient and want to populate the tank with other types of fish immediately. Remember, if the fish that you add to the tank cannot tolerate the peaking levels of ammonia and nitrites, they will die. Sometimes they will be dead the next morning, and sometimes they may survive for a month or more, but the damage has been done and they will ultimately succumb to the toxic affects that the ammonia and nitrites have done to their internal organs and gills. Do yourself a favor and have the patience to do it right.
All of that being said, many aquarists (including myself) use a simple trick to speed up the conditioning process. If you know someone who has an established, healthy aquarium, (the key here being healthy) you can take a scoop of their substrate material and add it to your new substrate. The gravel taken from the established tank will be teaming with these bacteria and they will grow rapidly and spread into your own substrate. I will emphasize again; make sure the tank you are taking this gravel from is healthy. Home aquariums are a small, enclosed eco-system and anything, good or bad, that you take from their tank will end up in your tank. Keeping this in mind, I highly recommend that you do NOT take established gravel from a pet store to help speed up your conditioning process. You never know what animals, healthy or otherwise, have been in their tanks. Whatever those animals had will likely be in the substrate and will then be transferred to your new "pristine" aquarium. Definitely not worth the risk.
Jon Stepp is the owner and author of SuperPetGuide.com Feel free to visit his free website to learn how to setup and maintain a successful Saltwater Aquarium [http://www.superpetguide.com]
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