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Live Rock


Dear Aquaworld,

Buying live rocks for a reef tank. What are the things to look for in buy in live rocks? Do's and don'ts for a reef tank?

Winter Garden, Florida, USA


Dear Drew,

Bubble Aquarium.

Live rock in a bubble aquarium.  Sometimes you can find live rock with macro algae growing on it, as in the case of the red algae in the upper left side of this aquarium.

When buying live rock for a reef tank it is always best to buy cured. What is cured live rock? When live rock is shipped from the collection site, whether it is from Florida, or Fiji, it is always shipped in a cardboard box without water. Live rock can be in these boxes for several days before it makes it's way to your local fish store. Many organisms (algae, sponges, worms, small inverts, bacteria) will die while being out of the water for such a long time. Many of these dead organisms are buried deep inside the rock. When these new rocks are placed in an aquarium the ammonia and nitrite levels can rise quickly from these decaying organisms, killing all fish and inverts within a few days. It normally takes at least three weeks for the excessive ammonia and nitrite from these rocks to subside and the levels in the aquarium drop down to 0 ppm. Once the water in the aquarium reads 0 ppm ammonia and nitrite the rock is generally considered cured, but that is not exactly 100% accurate. It just means that there is enough nitrifying bacteria in the tank to keep the levels at 0 ppm. Always smell the rocks before you buy. If you get any whiff of a rotten egg smell, put it back and try another rock. The rotten egg smell is hydrogen sulfide, a good indicator that some more curing is needed.

Before you buy live rock from a store, make sure to ask if the live rock is cured. When you bring live rock home from your dealer, it will most likely be transported without water, therefore make sure you get the live rock home as soon as possible. The live rock will be fine as long as you do not keep it out of the water for several hours, and let it dry out, otherwise the curing process will start all over again.

The things I look for in live rock are any macro algae, coraline algae (purple calcareous algae), holes, and as much surface area you can get for the weight. Often dealers have live rock that came from another hobbyists reef tank that will be covered with coraline algae, if not some small button polyps and mushrooms. Look around, you may get some really great rock.

It is always best to start off a new reef tank with live rock first, before you add any animals. Once you get the live rock home, make sure you place the live rock in contact with the bottom glass of the tank, and then pack any sand around the rock. This will help prevent live rock from shifting if you happen to put a fish or invert in the tank that likes to dig. Once the rock has been in the tank for three days check the ammonia and nitrite levels. If there is any ammonia or nitrite after three days, the live rock is not completely cured. Monitor the ammonia and nitrite closely, and do not add any animals until the reading for both is 0ppm.

Tony Griffitts

Published - 20070828

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