007: Curing Live Rock And Cycling Your Saltwater Aquarium

Once your tank is up and running it’s ready for life, although maybe not the life you’re thinking of. Every aquarium, whether it be saltwater or otherwise, requires a large amount of bacteria to function. These beneficial bacteria will consume the toxic waste products produced by the inhabitants of your tank and convert them to less harmful substances. The best way to establish sufficient quantities of beneficial bacteria is with live rock. Live rock is essentially pieces of rock that have broken off of a natural reef, typically during a storm. While technically not absolutely necessary, the use of live rock in your saltwater aquarium is highly recommended. Not only does it contain tons of beneficial bacteria that will go a long way towards keeping your water pure, it also contains a myriad of other critters and algae. This additional life is not only interesting and beautiful to look at but also will provide your tanks inhabitants with a steady source of food. Finally, live rock provides your fish with a familiar and natural environment which will help keep them happy and healthy.


The only problem with live rock is that, since it often travels halfway around the world in nothing more than a bag in a box, a lot of the life residing on and in it dies by the time it gets to you. Luckily this problem can be overcome through a curing process. Since your tank is new and doesn’t contain and fish or invertebrates yet your live rock can be cured right in the aquarium. Make sure you never do this in a tank that’s already inhabited as the water will become quite unsuitable for life temporarily. Doing the curing in the tank will also help establish any other biological filtration media at the same time as well as break in the protein skimmer. The whole process should take a few weeks.


Live rock is typically sold by the pound. Since the rock is a natural product it can be hard to figure out exactly how much you will need. However, around one pound per gallon is a good starting point. Some pet stores carry fully cured live rock which is great if you don’t mind paying a bit extra. Otherwise, you’ll need to order it through a pet store or online. Before it arrives you’ll need to gather a few supplies including a bucket for water to give the rock an initial cleaning and something to scrub the rocks with such as an old toothbrush. You may also want some gloves.


Once your rock arrives the fun can begin. Fill the bucket about halfway with water out of the tank. Then, using the toothbrush, thoroughly scrub each rock and rinse if off in the bucket. Try to remove anything that appears to be dead or dieing on the surface of the rock. The live rock will likely have quite an unpleasant smell which should go down as you clean it. Once each piece of live rock is as clean as you can make it you can place it in the tank. Don’t worry about getting them set up in their final arrangement at this point. Instead focus on stacking them very loosely and open to allow lots of circulation. You’ll likely need to pull more water out of the tank as you add more rocks. Use it to replace the water in the bucket as it gets dirty.


During this curing process the lighting should be left off. At this point all it will do is encourage undesirable algae. The protein skimmer, however, should be running full time as it will be doing a lot of the work. Initially, it may need to be closely monitored and adjusted as it will be pulling a lot of gunk out of the water for the first few days. Continue to lightly scrub the rocks with a brush daily to loosen dead material. Water changes will need to be preformed about once a week. Aim to replace around 50% of the water. When siphoning water out of the tank, try to suck up and detritus that has settled on the bottom as well as on the rocks. Since the aquarium now has something in it the water will need to be mixed somewhere else prior to changing it, such as a bucket or large plastic tub.


The tank water’s parameters will need to be tested weekly to check on the progress of the curing process. During the first week the ammonia level should gradually rise then fall. Around the time the ammonia level begins to fall the nitrite level will in turn begin to rise. Once the nitrite level begins to fall the process is nearly complete. Continue to monitor the level of both ammonia and nitrite until they fall to zero. At this point perform another 50% water change, trying to suck out any remaining detritus on the bottom, and allow the tank to settle for a day or so. Test the ammonia and nitrite one more time to make sure they have remained at zero. You can also test the pH and nitrate level to ensure they are within the acceptable range. At this point your live rock can be rearranged into the desired formation.


With the rock fully cured and in place you can begin thinking about what type of substrate you wish to use. While a saltwater tank can be run just fine with a bare bottom most people prefer some type of substrate, such as sand. Marine substrates come in a lot of varieties with a range of colors and sizes. Your choice may be influenced somewhat by what you eventually intend to keep. Some burrowing fish, for example, need a particular particle size. Ensure that the substrate you choose is approved for use in a marine environment. Live sand is also available which, much like live rock, is harvested from the wild and is loaded with lots of bacteria and other microorganisms. Unlike live rock, however, live sand doesn’t typically require as lengthy a curing process.


Whatever type of substrate you choose the process of adding it to the tank is the same. First, place it into a bucket and add some water from the aquarium. Gently stir the substrate until the water turns cloudy. Drain away the water and place some of the substrate back into the bag it came in. Then lower the bag slowly down into the tank and gently pour it out into the tank. Repeat this process until you have all the substrate in the aquarium. Finally you can gently spread the substrate out around the rock. Using this method you should be able to avoid stirring up too much dust into the water. Even so, the water will likely become somewhat cloudy. Just give it a few hours and it will settle back out. With the rock and substrate in and cured your tank is one step closer to being complete.

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