Docker-compose - use existing network, mariadb?

Hello - I’m hoping to run a seafile container; the docker-compose.yml example on the installation page is my guide. However, I already have a mariadb container, whose service is called “mariadb”. Can I use this for seafile? And can I use an existing network (I have two: “internal” and “external”) for seafile, or does it need its own dedicated network (“seafile-net” in the docker-compose file)? Many thanks!