Welcome to the forum.
It sounds like you have had a lot of experience with all kinds of pets. It is good to have you here.
Yeah, one of the things pet owners tend to overlook is the size of adult pet. They often judge the requirement for the pets based on the current size rather than the potential full size. In the case of fish, it is important that we have to get fish tanks big enough for the full adult size of the fish we plan to get.