Stocking questions!

Edit ORA mandy's are mandarins from ORA.
My suggestion albeit expensive, Upgrade your tank.
This is going to be your hobby. You are going to want to keep fish you like. Dont limit your selection to the size of tank you have but find what fish you want and design the tank for them. By your questions you seem to like active swimming fish and fish that require bigger tanks. Watch CL i see tanks go for cheap on there all the time.
Just my 2 sense

 

ORA mandarins aren't any more guaranteed to eat prepared foods than others. Many people buy them thinking that and find out different when they get them in their tanks. They're always going to prefer the copepods.

 

That's too bad. They are just so beautiful. They are dirt cheap too! (non-ORA) they should stop selling them or require a permit. I had a regular one a long time who when I didn't know. It did eat mysis though. Maybe the gramma