It is very hard to suggest which fish to add without knowing basic information about the fish tank. There are over 1,000 Cichlid species from around the world that get different sizes, compatible with different fish, and require different parameters - saying that you have a fish tank with Cichlid's does absolutely nothing.
As everyone else said Pacus get very big and 75 gallon, they simply get too big. When you said you moved the Pacus fish you were asked where did you move them and you never answered. I am sorry to say this, do not take this the wrong way but many people do not want to take advice and just say they "moved" the fish but did absolutely nothing.
Knowing the type of filtration helps a lot as well, if you have a strong filtration system you will get away with overstocking your fish some-what.
Finally, I suggest you go with common Mbuna African Cichlids; they are small, there is a huge variety, generally are kept in large groups, and are very fun to watch.