I use selco (which is a selcon like product) for my G. chiragra mantis shrimp and it definitely does increase apatite by a noticeable degree, selcon and selco are almost universally recommended for mantis shrimp, especially in larger species such as O. scyllaris because in some studies it has shown to help reduce the occurrence of shell rot, especially in larger or older specimens, i imagine if it has such good results for mantis shrimp that these benefits transfer to fish as well considering it is a nutrient booster which should be pretty universal in its effect.