Pretty tank! and yes, you will need to upgrade! The general rule is a gallon fo water per inch of fish (you can break it, but it gets tricky,, i have tried and decided to stay with the rule) and mollies get anywhere from 2.5-6 inches! (sailfins get huge!) and the pleco will be 18-24 inches... the gaurami will be the little guy, at 2 inches.

very pretty though