Decorations
Next, consider the decorations, of which there are a cornucopia of choices. Dead coral, lava rock, tufa rock, live rock, and many more. Coral pieces are the most popular, but are also some of the most expensive. Lava and tufa rock are inexpensive and may also be stacked to make interesting reef looking tanks. Live rock is one of those buzz words that people like to throw around and one which gets a lot of hype. Live rock is simply rock taken from a reef system which has been populated by many different organisms.
Live Rocks: A natural environment
Many aquarist dedicated to fish-only setups are beginning to discover the benefits of having live rock in their system. Live rock produces a more natural environment for the fish and also aids in nitrification and de-nitrification. This implies that the live rock is more that just a decoration, it is actually part of the filtration system. Although it is difficult to use live rock as the sole source of filtration in a fish-only setup, it certainly can be used effectively to reduce nitrates. The use of live rock in fish-only setups must be closely monitored though. If nutrient levels in the aquarium are high, the live rock will be the first to demonstrate this fact. Live rock in presence of high nutrient levels will grow unhealthy amounts of hair algae, and in some cases, cyanobacteria (slime algae). To avoid outbreaks of plague algaes, a few simple rules must be followed.
First, you must start will high quality live rock; live rock which is highly encrusted in coralline algae. Avoid live rock which already has hair algae growing on it. Regular additions of calcium may also be needed to keep the coralline algae thriving. Next, you need to keep nitrate levels low (~10ppm) and ensure you have nearly undetectable levels of phosphate (~0.02 ppm). Finally, feed sparingly; decomposing food is one of the main avenues for introducing phosphate/nitrate and contributing to alga e problems.
If you plan to add live rock to your system, remember live rock contains living organisms, so they can be killed along with any other organism in your tank. It's a good idea to wait until after the tank is set up before buying live rock. There is no good place to store live rock other than in a circulating tank. Trying to do otherwise will be disastrous and costly. Also, if you are going to put live rock into an established tank, the rock must be cured live rock.
