The aquarium is in position and equipment is available. Now comes the most exciting part of all, building the reef and stocking. Reef construction first, of course.
The aquarist may have decided that live rock is just too expensive at the moment and has decided to use an alternative bio-filtration method. In this case the cost is going to be greatly reduced. The rocks purchased will need to be inert (ie. marine safe) and it is unlikely that any marine retailer will sell anything that isn’t.
Before the aquarist jumps in and buys some rock, remember that corals are going to be added and corals normally come attached to rock. This rock will be from the ocean and may bear life forms similar to live rock. It is to most intents and purposes live rock. Perhaps the rock purchased for the reef can be those which are highly porous. If this is the case marine organisms will in time establish homes in and on it. In time it can even become live as bacteria make a home.
On the other hand, the aquarist may have decided to use live rock. The price may have been high, but nevertheless that is the road chosen. There is a way of reducing the cost and that is to buy less and use safe porous rock as well. The proportions can be ½ and ½ or more, that is more live rock. It is worthwhile purchasing premium live rock so it can go on the reef surface, and it is spread reasonably equally over the reef. In time the porous rock should take on marine life and become live. The only potential problem here is the initial bio- filtration. Reef systems, with a view to water quality, have a lower fish load and the bio filtration should initially cope, and with slow stocking the capacity will increase. The aquarist must be aware that the initial bio-filtration is lower and keep an eye out for problems. On initial start up water parameters are regularly routinely tested anyway.
Perhaps the aquarist is going to use all live rock. The usual guideline for the amount of live rock to use is 1 to1½ lbs per gallon of the whole system net gallonage. This is fine, but a problem arises because some live rock is considerably lighter than others. So a different guideline can be used and that is that the reef should be around 2/3rds of the capacity of the display tank. This is often the amount that is to be used anyway to create an attractive reef, and offers the aquarist room to aquascape and also leaves water space for fish. Costs can be reduced with all live rock by buying premium rock to cover the outer reef and base rock for the foundation.
The following is a personal view. Many aquarists place their rocks directly on the aquarium base. I prefer to raise them above the base, say 1″ to 1½”. This allows water to easily access the area. The job is very easy and cheap using plastic ’egg crate‘. (See the text ‘Elevate Your Reef’ under DIY.)
Whether the rocks are put on the aquarium base or not, and whether the rocks used are live rock, a live/inert rock mix, or all inert rock, the following applies. It is important that the rocks are not ’fitted’ together too tightly. Accurate fits are not possible, of course, as the rocks are pretty random in shape. The rocks of the reef should have gaps and tunnels throughout, and their random shapes should assist with this. Having good gaps and tunnels allows water to flow throughout the structure more easily. If there is good water flow then there will not be any area lacking in oxygen or even stagnant. The spaces between rocks afford livestock plenty of hide holes. The rocks also need to be stable to avoid any rock fall.
Putting the reef together can be great fun. When I did mine, I started again at one point, even though most of the rocks were in the tank. Eventually, I achieved what I wanted, and also managed to make a couple of small caves within the structure. I know that the Flame Angel uses one at night.
Particularly with live rock, but also with other rock if desired, it is advantageous to have the aquarium say 2/3rds full of prepared seawater which is heated to the desired temperature. As the rocks go in the water rises. When the rock work is complete if the water is short of the required level it can be topped up. The circulators can be turned on and there’s the reef.