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Coral Reef Keepers
1381 Plank Road Suite 98
Duncansville, Pa 16635

Fax: 814-695-5114

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Thursday and Friday 3 to 7PM
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Cycling a Saltwater Aquarium PDF Print E-mail
Wednesday, 30 May 2012 15:00

Why Understanding the Nitrogen Cycle is Essential to the Health of Your New Fish


A properly cycled marine tank isn't just important; it's an absolute necessity! And a properly cycled tank really tank can mean the difference between your success and failure.

One author put it this way: Imagine for a moment that you are given a sterile glass box. Now fill that glass box with saltwater. Pretty, isn’t it? The water virtually sparkles because it is so clean and clear and crisp. Now imagine heading down to Coral Reef Keepers and buying a clownfish and putting it in your glass box. At first the clownfish seems quite happy, but then, it starts to look more poorly. What’s happening?

Believe it or not, we received a call from a woman asking about our guarantee on our clown fish. We stand behind our fish of course, but we wanted to know more about her tank. “Well, I've just set it up.” Her tank had no live rock, no live sand, nothing to break the wastes down. We explained that the fish wouldn't have a chance to live very long – guaranteed! By the way, she never came in.

Sterile Tanks aren't Good for your Fish

The reality is that a tank is like a toilet for your fish, and beneficial bacteria are necessary for breaking fish wastes down into less (or non-) toxic wastes. In a mature (or “cycled”) tank, beneficial bacteria break down fish waste before it reaches toxic levels. While you still need to perform regular maintenance and use a reliable filtration system, the fully cycled tank is a much more stable environment and one that will allow fish to live.

What does “cycling a tank” really mean? The phrase “cycling a tank” refers to the nitrogen cycle where fish waste (ammonia) is converted by bacteria to nitrite (NO2) and then the nitrite is converted by other bacteria to nitrate (NO3). Nitrate, unlike nitrite, is much, much less toxic than ammonia and, providing you do regular water changes, nitrate will not build up to levels toxic to your fish. In a cycled tank, there is a sufficient amount of bacteria necessary to eliminate wastes. This is why we stress adding only a few fish into a tank at a time.

This also points to another source of tank problems – making too many changes at one time. We also stress making changes gradually. If you need to change water, change 10 to 20 percent. If you need to change substrate, change a small amount. If you need to clean filters, clean them (but not too well) in saltwater. Remember: The key word is gradual. You'd be surprised how many changes you can make in your tank. But all change has to be gradual.

The Best Way to Cycle a New Tank

At Coral Reef Keepers, we believe that the best way to cycle a new tank is by adding live rock. Live rock is not actually alive, of course, but it comes from the ocean (either aquacultured or from reef rubble zones). In either case, it's full of life. During the process of getting the live rock from the ocean to your aquarium, a certain amount of life on and in the rock will die. When you add this live rock to your new aquarium, it will prompt the nitrogen cycle as the dead and dying organic matter begins to decompose providing ammonia for beneficial bacteria.

Over the course of the next two to four weeks, the rock will and the tank will cycle. During this time, it is important to krrp your filter running on your tank and insure that strong flow keeps detritus from settling. And do frequent water changes too. This cycling process can be smelly, so don't be surprised if your tanks smells something less-than-pleasant during this time. For this reason, some people choose to cure their rock in a separate container in the garage (a trash can with several powerheads and a heater will suffice). If you do cure the rock elsewhere, you will still need to still cycle the tank when you add the live rock after it has cured.

How Do You Know When Your Tank Has Cycled?

The only way to know whether or not your marine aquarium has cycled is to monitor the water quality. Coral Reef Keepers sells a simple test kit for measuring ammonia, nitrite and nitrate. While we can test for you, you'll achieve the best results by testing daily. You will notice an initial spike in ammonia over the first week followed by a spike in nitrite toward the end of the second week. When you have recorded these spikes in ammonia and nitrite, you need to wait until both fall to zero. When they do, your tank is cycled, and you are ready to start adding livestock.

Some Final Thoughts

Is a properly cycled tank going to stay “cycled”? It all depends on you. When you add livestock to your tank, you could initiate a mini-cycle, which is why you should only add a few fish at a time and wait for ammonia and nitrite to fall to zero again before adding more fish.

Some stores recommend cycling a tank with blue damsels. There are at least two reasons we don't do this. One, it's pretty inhumane to dump a fish into clean water and expect it to live while the tank cycles. And two, damsels have earned a nasty reputation for being aggressive towards other fish. While some are friendly, many aren't. And once they're in a tank, they're almost impossible to remove!

Remember: Each tank is different, and cycling times will vary depending on the quality of the live rock and many other factors. Make sure you to monitor the water quality by testing it. That's the only way to truly know if your tank has cycled.

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