Hello Forum Newbie

Welcome to the forum, Mims !
Good to read of your tank inhabitants.
Re the missing betta, have you taken a good look under your tank and specifically at the corners of the skirting boards or where they border furniture, and behind the filter?  In my experience, fish have mysteriously ended up both behind the filter (despite a gap of <1mm) and on the floor despite a tight-fitting lid (one species was especially prone to this).  Be careful when removing the filter - best to pull it away from the glass to give the opportunity for him to float out from behind it rather than risk squashing him.  Hope he turns up, ideally still alive.

Welcome Mims!