Live Rock

for the week of 7/29/99

Many saltwater novices look twice when they see a sign for “Live Rock” – and then look a third time when they see how much it costs! Live rock has become the heart of many marine systems, including both reef and fish-only setups.

Live? – The rock itself isn’t alive, of course, but it does contain various bacteria, algae and other microorganisms that are beneficial to aquariums. As they do in nature, these organisms consume waste, produce oxygen and even provide a food source for grazing fish. In many reef and simple setups, the live rock performs all the filtration, with perhaps a protein skimmer to help out.

Cured vs. Uncured – Live rock can be purchased either cured, meaning it was held somewhere for a few weeks, or uncured, meaning it wasn’t. During the curing process, some damaged or unsalvageable life forms perish, and the curing container becomes cloudy and quite smelly. It is obviously never a good idea to put uncured rock into a display tank. When everything that is going to decompose has done so, the rock is “cured” and ready for use.

Atlantic, Pacific, Fiji, and Cultured – Live rock can come from a number of places. Atlantic live rock was once common in the hobby, but now collection is illegal in American waters. In addition, Atlantic rock was very dense, meaning one would need twice as many pounds of rock for the same visual effect. Most of the “wild” live rock now comes from the Pacific, and the most common type comes specifically from Fiji. This rock is less dense, has a lot more interesting shape, and usually carries a fair amount of encrusting algae. Newer on the scene are cultured live rock; a few companies are now seeding a part of the ocean floor or huge tanks with plain rock, allowing it to become covered with life, then harvesting it for sale.

Base Rock vs. Decorative Rock – Base rock is generally devoid of any visible life forms, but contains plenty of bacteria and other microbes that make a tank healthy. It is generally used as the foundation, or bottom layer of rock, and more decorative pieces with encrusting algae are placed on top.

Making Your Own – Any rock will eventually become “live” in an aquarium, and it’s possible to buy dry, cheaper rocks (porous stones like Tufa Rock and Paradise Rock work best) and simply wait until it becomes colonized. This process takes several months, during which the tank is somewhat unstable and prone to unsightly algae blooms, but success can be achieved with a bit of patience.

“Tip of the week” appeared regularly in 1999 and 2000.