Will silver dollar fish get along with guppies?

Silver Dollars grow to over 12 inches long and could well eat a guppy although they are normally vegetarians. You need a minimum size tank of 30 gallons to keep a couple of silver dollars. Please follow the basic rules. :- 1 inch of fish needs a minimum of 1 gallon of water. :- Every tank needs a permanently running cycled filter. :- Every tank needs at least 50% of its water changed every week. Keep the above rules and your fish stand a chance. Fail in any of them and I can guarantee that you will have constant health problems with your fish.