The following excerpt has been taken from the Reef Notes series of books featuring questions answered by Julian Sprung and have been printed here with his full permission. Please check back frequently as we will be adding different topics on a regular basis. All previously printed topic will be held in an archive link.

Topic: Dead Coralline and Tufa Rock in the Reef Aquarium

Q: I am going to use dead coral as a base for my live rock. Is this a good idea or do you have a better idea? How often and how much live rock can be put in at one time?

A: There are many questions which don't have a clear-cut yes or no answer, and your first one is one of these. I can tell you that my usual response to this question is that using dead base rock won't result in some horribly disastrous explosion, and it is true that invertebrates and algae will spread and colonize the "new territory," but I still prefer to create a reef tank using all living rock. It is not true that underlying rocks "will die away" as I have heard my uninformed hobbyists preach. Good quality rock will have encrusting sponges and coralline algae that will proliferate beneath, and between, the rocks. It is hard for me to explain exactly why I prefer to use all living rock considering that recolonization occurs, but I'll give it a shot. First, each live rock you purchased already has been colonized by an enormous variety of bacteria, protozoans, invertebrates, and algae, while a mere fraction of these are manifest as a result of the particular environmental conditions (temperature, light and water movement, nutrient supply, etc.) that existed where the rock was collected. Each rock, therefore, has a potential to produce a lot of life. The less live rock you use the lower that potential production is, and the colonization onto other rocks which occurs is limited to far fewer species that can exist on a single live rock. I have noticed that aquaria using all live rock have a greater variety of algae and invertebrates, and that the source of the rock (shore versus reef) makes a significant difference in the ultimate captive reef produced. Finally, I suspect that starting out with all live rock has further advantage in the production of an actual plankton cycle involving bacteria, protozoans, algae, crustaceans, various, invertebrate larvae, as well as invertebrate-generated detritus and plant detritus with attached bacteria and protozoans. This cycle is natural and perpetual and, in my opinion, sufficiently meets the needs of most filter feeding invertebrates without the need for supplemental additions. Every reef keeping aquarist have his or her own recipe for adding rock to the aquarium.

When fresh live rock is received, each rock should be carefully cleaned by vigorous shaking in saltwater (never ever put a live rock in freshwater) and stripped off all macroalgae. I do not recommend scrubbing the rocks as common practice since I believe that many desirable species could be lost this way. Scrubbing is only useful in the incidence of fouling. As a point of interest, most of the algae species stripped off by hand will grow back under proper conditions, even if the rocks are kept in the dark initially for many months.

If the rock is fresh and the algae is not excessive or rotting, it can be left alone (don't strip off plating red coralline algae) and of course the rock can be illuminated. Rocks with zoanthids or coralimorphs (i.e. Ricordea Florida) definitely should be illuminated. Some aquarists misunderstood my recommendations here, which were for those rocks used to build the reef structure on which one wants to encourage proliferation of coralline algae.

Most notable is that you have used dead based rock to build your reef. A few pieces here and their to prop up a specimen or live rock is ok, but when dead rock is used as the principle base structure, hair algae is difficult to avoid. Hair algae "likes" to grow on bare limestone rocks, like tufa, and perpetuates its presence on these rocks by trapping nutrient rich detritus in the network of its tangled filaments. Also, the porous structure of tufa tends to trap detritus and encourages algae growth. Live rocks have encrusting coralline algae growing which effectively retard the growth of hair algae on the rock. If the corallines die, and bare limestone is exposed, the hair algae has a chance to gain a foothold, but it may not since there are also tiny flea-like crustaceans called amphipods which live on the rocks and come out at night to graze on algae.

To maintain good growth of coralline algae, you need to maintain a calcium level of at least 400 mg/l, a hardness of 7dkh or higher, and keep up with your strontium additions. Ideally you should be making Kalkwasser by adding a teaspoon of calcium hydroxide or calcium oxide to each gallon of your make-up water, and adding this solution slowly to the tank by means of an automatic water make-up system or by a drip system.