Stocking help?

[Mashpotatoes74402]

So I've got a 75 gallon set up months ago and cycled
I've got two magnum 350/a running
Filter one is mech and Chem.
Filter two mech and bio
Instead of normal filter media the whole canister is full of ceramic rings

So I've got 150% of recommended filtration
My current stock is
1 - 2 in Oscar ( that's why this is difficult)
3- 2 in silver dollars
1 - 2 in crayfish
6- mystery snails
I'd like to add some more colorful fish
Because the silver dollars are always hiding. And the Oscar is always chillaxing. He only swims around duri feeding times
Could I add more silver dollars to make the school "braver"???
Or maybe some colorful cichlids? I u derstand the crayfish might get eaten. I usually dump 12-20 ghost Shrimp in weekly too

 

[torres]

Silver dollar is always hiding because you should have at least 5 of them!

 

[Mashpotatoes74402]

So a bigger school??? I'll check into that

 

[Mashpotatoes74402]

What's a good sized school? And. An I mix young and grown silver dollars? The ones I have are twice the size of the ones for sale at my lfs