Polyurethane Foam

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Some large public and private reef aquariums in Europe have very little limestone rock at all in them. What looks like rock in these tanks is actually a polyurethane foam substance which has been shaped to look like rock. The surface is apparently very attractive to coralline algae which rapidly colonize it, making it virtually indistinguishable from the "real McCoy." The Aquaria-Vattenmuseet in Stockholm, Sweden, Hagenbeck s Tierpark in Hamburg, Germany and the Lobbecke Museum in Dusseldorf have large reef displays with such material used as a substrate. We do not know much about the material or whether it can be acquired easily, but it may be an important aspect of large public aquarium reef displays in the future. We caution aquarists about the use of such materials because of the possibility of toxic compounds leaching into the water. The success at the aquariums mentioned above, however, indicates that acceptable inert versions of these materials do exist.


Some ceramics are also a suitable material for building reef structures, though we caution that heavy rocks should not be supported by ceramic pots or forms. Some ceramics may leach harmful substances into the water, but most are inert when fired. Ceramic rock forms have good potential for reef aquarium building, since they would be porous like limestone, and the shapes can be quite marvelous.

Materials That Facilitate Reef Construction

Cable Ties

Solid plastic cable ties, commonly used by electricians and mechanics to secure bundles of wire, also have great use for securing rocks together when building the reef structure. These ties seem to have a million uses! Cable ties come in a variety of lengths and thicknesses, and in either opaque white, grey or black. Caution: be sure that the ties are solid plastic. Some ties are made with a metal core.

Alf Nilsen shows how it's done! He uses plastic cable ties to secure the live rock structure in a large reet aquarium in Oslo, Norway. Courtesy of A.J. Nilsen.

Close-up view ot a gorgonian, Pseudopterogorgia sp., that has been attached to a live rock by means of a plastic cable tie. Coralline algae and the gorgonian's tissue have already grown onto the plastic, obscuring its presence. J. Sprung.

Tropical Coralline AlgaeCoraline Algae Styrofoam

After planning the layout of the reef structure and selecting the rocks, a drill and masonry bit can be used to bore holes into the rocks to slip the cable ties through. Be careful when drilling holes, since limestone rock is brittle and easily crumbles from the vibration oi the drill. Do not drill holes too close to the edges of rocks. The leverage of the attached rock pulling on the hole near the edge of another rock can cause the cable to break through the hole, sending the rock(s) tumbling. Cinch up the cable ties tightly, and cut off the end with a sharp scissors. In one aquarium in Norway, a wooden beam across the top was used to support large rocks, forming an otherwise impossible overhang/cave. The rocks

Pvc Aquarium Cave

Kjell Nagy's aquarium, Flekkefjord, Norway. Note how PVC pipe, wooden beams and cable ties are used to create a cave and overhang. J. Sprung.

were tied to each other and to the beam with long, heavy- duty plastic cable ties. Cable ties may also be used to attach the uppermost rocks of a wall to plumbing along the back or sides of the tank, thereby affording greater support.

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  • matteo
    How to make urethane foam look like limestone?
    8 years ago

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