Choosing the right live rock for your nano reef is very important. It will be your main source of biological filtration, and will create the entire look for your nano reef. There are many different types of live rock to choose from, but all will do the same thing. When looking for sizes that suit a nano reef, many people will use just one large, nice piece, or lots of small 'rubble' pieces and build it up. There are three main types of live rock available to the hobby today; Pacific, Atlantic, and Aquacultured. The following will help you know what to look for as you select the right live rock for your needs.
Pacific is the most common live rock that hobbyists choose. It is very porous, light, and usually colorful with coralline algae. This live rock also has many different shapes. You will hear Pacific live rock called many different names; fiji, hapai island, samaoan, tonga, marshall island, vanuatu, etc. These names refer to the island region that it was collected from. The shapes and density may vary from region to region. When picking, choose nice pieces that you like, and try to get 'cured' rock, because it is less likely to have pests in it. A good rule of thumb is to have 1-1.5 pounds per gallon.
Atlantic live rock is becoming less popular. It is generally dense, and the shapes are not as interesting or intricate as Pacific rock. The advantage is that it is quite a bit cheaper. The pieces are just as life covered and coralline encrusted as Pacific rock too. This rock usually comes from the Gulf of Mexico. When selecting Atlantic live rock, look for smaller pieces and ones with more holes or features. Because of the density, at least 2 pounds of Atlantic live rock should be used per gallon.
Aquacultured rock is still new, but becoming very a very popular alternative to 'wild' live rock. Aquacultured live rock is created when regular dry rock is placed in the ocean and then harvested many years later. The shapes and sizes all depend upon what rock the creator used. Some rock can be rather plain and bulky, while some are quite porous and nicely shaped. Much of the aquacultured live rock available is good because it is pest free, so you won't have to worry about things like bristle worms and mantis shrimp. The best thing to do when choosing an aquacultured rock supplier is to get opinions from other hobbyists. See if their rock was pest free, if it looked nice, and if it had lots of life on it. Depending on the density of the particular rock, use 1-2 pounds per gallon.
Cured & Uncured Rock
When all liverock is collected, it's usually cleaned off with some brushes and rinsed to remove any mud that might be on it. It's fresh from the ocean and usually crawling with life. Crabs, shrimp, corals, and macro algae are present. Not all the animals that are in the rock are wanted however. Pest anemones and mantis shrimp are the two most common pests on live rock. Uncured rock basically comes to you in this state. Cured rock goes through a longer process to help 'clean' it up a bit. It's often times kept in vats which are cleaned out regularly to allow time for some of the dead things to be removed. Other methods of curing involve the rock being sprayed with a higher salinity saltwater to make some of the pest animals run out, and remove any die off. Cured rock usually costs more.
So which should you buy? It doesn't particularly matter which you chose, but there are some benefits to chosing one over the other. With uncured liverock, you're going to have a lot more life present on the rock, and maybe even some hitchhiker crabs or shrimp. But with the good comes the bad; uncured rock is more likely to contain pests, and usually will take longer for the tank it is placed in to cycle. Cured rock is less likely to have pests in it, and aquariums starting off with cured rock have a shorter cycle time.
Always choose the rock you like best. Your nano reef is your own creation, so make it look however suits you best. Since you don't need a lot of rock, be willing to spend a bit more money on cured, quality live rock. Also remember that live rock that has already been in an aquarium is better than rock that is fresh from the supplier, or shipping box, because it is likely to be free of pests and die off from transit.