For small fish I wold isolate them in a cubicle system. This keeps em from fighting and the jumpers from jumping (until you open up to catch em). The problem with multiple fish in a tank is something I learned that the hard way. I am going to isolate the small ones in a remodel coming up soon. I think about 15 4x4 cubes, 15 6x6, and 15 8x8 cubes are a good way to go(that about 45 small fish to isolate but some can have multiples such as clown gobies). If no one out there does acrylic systems like this, you might consider 2.5 gallon glass tanks. Then for the medium fish 20 Gallon tanks would be good, and then 60 gallon tanks for the larger community fish. For corals just do an overview system like a zero edge aquarium or something, really shows off the corals well. Now for plumbing you will want 2 salt systems, one for coral and one for fish (so fish can be medicated). For fish system, the skimmer I would recommend is RK2 with a large sump, a UV sterilizer with 0 bypass, a sand filter, deep sand bed filter(in sump), and lots of live rock. For corals, simply a large sump, lots of live rock, ozone, and decent skimmer like a large octopus, deltec, euro reef, etc. Budget is the main issue though.....