I was playing on Hard, and i used 2 Monkey Engineers with Sentry Guns on the first rounds. The bloons on the later rounds mostly never were actually visible because they got popped before they even got a chance to appear. I used Dart Monkeys, Monkey Pirates, the Aircraft Carrier, Monkey Villages/Towns and Banana Farms/Republics. Only the M.O.A.Bs and B.F.Bs and Z.O.M.Gs appear but because of the pirates they just go down easily. Also using Bloonchipper to suck up bloons (since i don't have the MOAB suck up upgrade). But again, this might be OP.