I don't have any experience with them, but I'm under the impression that they are not really sand sifters. Phylogenetically G. brasiliensis and a few other related species (e.g., G. iporangensis, etc; the so-called "G. brasiliensis complex") are actually fairly distantly related to your "normal" Geophagus (e.g., G. altifrons, etc). I don't think they'll get hurt without sand.