Hi SuperSlow, and welcome to the forum. Your tanks look great, and your bettas are very pretty.
I would strongly advise rehoming the tetras now, if you can. They are active fish, and really should be in at least a 20 gallon. Having them in the 5 gallon is doing three things:
- overloading the bioload of the 5 gallon, as there are too many fish in there;
- not giving the tetras adequate room to swim;
- not allowing them to fulfill their schooling needs.
These problems are going to result in stressed fish, and stressed fish get sick more easily. Rehoming them to someone with a 20 gallon tank who can give them a full school would be in their best interests. :)