You said you got cichlids and pacu and yet the cichlids are small. So wth are you keeping rams and pacu? Throw some dovii, umbee, rd, jags, pbass they'll eat the minnows.
I had an arowana in the pond for a year or so and it disappeared. I think since it stayed right on the surface so much it was a great target for a passing Eagle or Osprey.
Just another thought on this. I spoke to a guy in Miami this week who is a marine biologist and has an acre of cichlids he breeds. He said not to get rid of all the minnows for two reasons:
1st when smaller shorebirds are after fish they take the easy route and go for the minnows and leave the good fish alone.
2nd. He said that most cichlids will survive on plant matter and algae butt when they need protein the readily available minnow fry are all they need.
I still think I have too many but I guess he has a point.