Following on from a previous recent article on reefland.com on rock, it’s possible to make your own, as described here with some of the issues often associated with the process. Of course, there are many methods, and aquarium hobbyists and professionals alike get a great sense of satisfaction from creating something that works. As I work in an aquarium, we’ve been in the position of having companies come in and create realistic-looking rock and tank interiors for us. It’s expensive, so doing it ourselves was a great learning experience and a big saving. Fortunately, the aquarium fraternity is a good one and there are plenty of people to help out with advice. We even sent some staff members to an aquarium in New York state to learn how to make tank interiors, which was a great help. So it’s worth a try, and it’s a great opportunity to do something different associated with your hobby.
Some aquarium hobbyists and professional aquarists like to do more than simply introduce, care for, observe and sometimes breed fish. While it is not a quick process, rock can be created to provide a substrate for a whole variety of living organisms in an aquarium. Live rock can be expensive – at between $5 and $10 a pound, with two pounds per gallon recommended, a 30 gallon aquarium can cost $600 to populate. Another huge factor in creating rock is that removing species, and large quantities of rock, from the natural environment, is damaging to the increasingly-fragile marine ecosystems. Many of the large public aquariums make their own rock, for these very reasons, and it can be made to look exactly like real rock, with few, if any, issues if created and cured properly.
There are as many methods for creating live rock as there are live rocks in aquariums. In general, the process includes making a mold, which can be in a box, or with chicken wire; mixing rock – including Portland cement, reef salt to increase porosity, and other ingredients – curing the rock, and then preparing it for the aquarium. The rock can then potentially become “home” to a whole host of organisms.
While there are many websites and even books dedicated to DIY live rock, the general rule of thumb is for standard rock structures and single rocks, a mix of one part Portland cement to two parts of aragonite sand to three parts of salt crystals. For branched rock, three parts of salt crystals is reduced to two.
Issues
Curing is critical, as the created rock should not cause any problems in the aquarium. This generally means that the aquarium water pH can be affected by chemicals from the rock leaching into the water. This includes phosphates, which can also be an issue if oyster shells are included in the ingredients of the live rock. Crushed coral can be substituted for oyster shells, and some low pH marine cement can assist in reducing the time of curing, which may take several months. Another factor in curing is that water the rock is left to sit in should be changed frequently.
Colonization
While introducing live rock adds a variety of species, both wanted and unwanted, an aquarium does require a great deal of diversity in order to create a balance. Live rubble, and/or a minor amount of live rock can be added and distributed throughout the aquarium, which is cheaper than adding all live rock and less environmentally sensitive. Adding other species, and coral, will also assist in increasing the colonization of the newly-created rocks.