Marking of skeletal body parts of marine animals with fluorochromes, such as tetracycline and calcein, can provide a valuable tool for mark-recapture studies. In recent decades, both fluorochromes have been used extensively for marking marine animals, including fish, mollusks, echinoderms and nemertean worms In this study, the authors examine protocols for administering tetracycline and calcein asmarkers for juvenile sea cucumbers.Wefocus on themost economically valuable of tropical species, the 'sandfish' Holothuria scabra Jaeger 1833, which is well suited to restocking and sea ranching. Experiments in tanks compared the efficacy of marking spicules and both lethal and non-lethal effects among different concentrations, durations and temperatures of immersion marking. Preliminary investigations of three additional fluorochromes, alizarin complexone, calcein blue and xylenol orange were also conducted to see if these would also mark spicules and potentially provide many dichromic marking combinations.