in a 75 gallon you probably won't be able to keep tankmates with a midas. you could probably do a pair in there but I'd have a tank divider in case the male gets too aggressive with the female.
A 75gal is too small for a full grown pair of Midas, the male would beat the female to death or at the very least, make her life very miserable. 75gals work for a solo adult Midas only.
You would defently need a larger tank,then add the other fish 1st,make sure the other fish are somewhat larger than the Midas,you may also want to try a "Red Devil"then you wont have to worry so much about size difference.Good luck!!!