As artificial rock becomes more prevalent within most fish stores and ‘used’ live rock is advertised all over selling websites and social media, it's important to understand the pros and cons of each.
Live rock has been around since we have had marine aquariums. It is one of the best filtration sources for a marine aquarium due to its porous structure, ideal for nitrifying and de-nitrifying bacteria as well as a host of microorganisms. Using a good quality live rock in a marine system from day one, can contribute not only the filtration capacity of many times that of modern media but also a great biodiversity. One of live rock's downfalls is that sometimes included in this rich array of life, comes not so desirable critters and creatures. It is common to introduce pests such as flat worms, bristle worms, aptasia, majano and nuisance algaes etc on live rock. You can minimise this risk by buying good quality rock from reputable sources and retailers.
I have seen second hand used rock on selling websites and, as it is cheap, it can seem like a tempting option for new hobbyists looking to start up on a budget. This can be a very problematic option though for several reasons.
Firstly, you don’t know where the rock came from and what issues the previous aquarium has had. For example, the previous tank may have had parasite problems and copper treatments. Copper is absorbed into the rock, deep into the pore structure and can leech out for a very long time. This can affect your ability to keep any sort of invert or coral.
Secondly, you are more likely to introduce pests, as used rock from an existing system is more likely to have hitch hikers on or within it.
Thirdly, you run the risk of nutrients that have been stored within the rock, passively leeching out for an ongoing period. The likes of phosphates can cause havoc, especially for new tanks, and lead to algae outbreaks.
Buying cheap, second hand rock that you don’t know the history of can end up costing you much more than the rock itself in terms of treatments and losing precious livestock.
Artificial rock has grown in popularity over the last few years, mainly as aquarists have tired of poor quality live rock but also because most of the man-made rocks come ready to go straight into tanks with no curing! In addition, you have zero chance of bringing in pests and nutrients within the rock. The downside is you have less biodiversity, although the rock will eventually turn ‘live’ with bacteria.
I used Walt Smith Reef Rock 2.1 in my new aquarium. It is already coloured purple from the off, so it looks great and it is easy to make some interesting scapes as the pieces all have individual shapes and sizes with no two the same. So far it has done a good job of processing harmful nutrients in my system.
The choice is up to you, but before you decide for sure consider this;
The very foundation your whole tank is based on is the rock and the ability to filter the water and provide a home for bacteria. Carefully consider what option is best you and start out on the right foot.