BigJay
Well-Known Member
this is a hard answer to give. But in general I like to look for.
1. Porous. The more pouros the rock the less water it displaces the less rock you need to buy to fill the tank. the more spaces for things to live. The more surface area for bacteria to form.
2. Life... I like to see fan worms, sponges , etc on the rock. If it has no life then its basically its not much different then dead rock that has been sitting in the tank long enough to pick up bacteria. Rock without life can surprise you though with things popping up months after being introduced. It also can be a catch 22 when you bring bad hitchihikers into the tank.
3. Color. Probably the least important but I prefer a rock that has good coraline growth. The rock generally will be purple but occasionally there are green coralines and red coralines. This must not be confused with nuisance algae which you never want to introduce a rock that has nuisance algae or bacterias growing like hair algae, bubble algae, or cyano. If you see rocks in the holding tank that have this algae you should be wary of purchasing any rock in the tank as spores may have already spread to the other rock.
4. shape and size. It must be condusive to your tank. Perfect looking rocks that have all the above but are too big or too small for your tank won't do you much good. Larger rocks can be broken apart but too many small rocks can lead to a avalanche waiting to happen and a many times an unattractive looking structure.
hope that helps.