Welcome to the site!!!
I think with blue rams you want at least a 20 gallon tank, for a matedpair. I think you'd have better luck with a kribensis which is hardier but you'd be able to have one pair and I think that would be it. Smaller tanks are harder to control water conditions and can be a damper for more sensitive fish.
You could look into nano fish such as celestial pearl danios, chili rasboras, to name a few. These are only suggestions keep in mind. It is your tank and I'm sure you want what's best for whatever you decide to go with