Tridacna crocea cultured grade A (blue) 6-8 cm , Tridacna crocea are relatively hardy clams, and require intense lighting and good water flow in the home aquarium. Proper water chemistry is very important, and they will thrive when calcium levels of 380- 450 mg/L, alkalinity level of 8-11 dKH, and magnesium level of 1280-1350 ppm are maintained.