By red tufa I'm assuming you mean lava rock, which is high in various metals that aren't desirable in marine aquariums. Reportedly white tufa, free of contaminating metals (ie. free of bands of colour) is reef-safe. I haven't used it myself, however.
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-Quinn
Man, n. ...His chief occupation is extermination of other animals and his own species, which, however, multiplies with such insistent rapidity as to infest the whole habitable earth, and Canada. - A. Bierce, Devil's Dictionary, 1906
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