Assuming the one you don’t like is the purple? Idk this brand, and don’t think a burn in period would help. Probably best to try and get a refund or replacement.
You could use glue or putty underwater, but will be difficult and putty will make your skimmer go crazy for a while. Just a note. Plan your aquascape with the idea of how they’ll hold corals for you not what the aquascape itself looks like
Ca reactor or kalk reactor will require special tools to make accurate holes. Then the challenge of making sure it doesn’t leak. Using it for what it’s used for or a media reactor is the direction I’d go. The effort isn’t probably worth the modification