I keep my tank upward to 1.025.
Honestly for a fish only setup you could probably range from 1.020-1.025 (keeping what ever range you pick consistant). Some people acutally leave their SG
lower than that in fish only setups because it lowers the chance of parasites since most dont fair well in low SG
I keep mine toward the upper end because I have corals and they are more sensitive to SG
your ok to keep it at 1.021 or go back up to 1.023. The key is more in keeping it consistant.