During the growth of L-arginine phosphate monohydrate (LAP) single crystals, the problems of coloration and microbial contamination of the solution were investigated. It was found that the solution coloration can be prevented by conducting crystal growth at temperatures lower than 40 degreesC and by inhibiting microbial growth. Compared to the known microbe inhibitors H2O2 and n-hexane, liquid paraffin shows advantages of long durability and convenience of usage for the growth of high-quality LAP single crystals.