Thought it was 150

The only way would be to remove inactive members. Keep people who have your Clan tags and are in the Clan, not just the group. Send them a personal message on b.net stating that the Clan is full and need to make room for active members, if they want to stay, tell them to please message you. Our Clan had to make sub-clans: SSE Alpha Co, Bravo, Charlie, etc. Everybody is part of the group StarSideEchoes, but then joins a sub-clan. All SSE's can see the Clan chat wall for SSE and see what others post, besides their sub-clan.

The maximum number of players in one clan is 100 but you can make another branch of the clan by making a new clan and naming it "raiding raiders uk" or "raiding raiders 2" or something