Big tank plan; little help?

[ElwoodPDowd]

So, I'm ready to commit to a bigger tank. I want something that's going to wow visitors. And I've got some questions.

It'll be a freshwater tank, probably filled with two schools of different tightly shoaling fish (love leopard danios, they look just like tiny salmon; undecided on what else) as well as a couple of centrepieces (probably a male betta of some sort plus whatever I can pick up that looks different, gets on well with everything else and won't uproot all the plants). There'll also be Zig, my inspector plec.

I love the idea of the sumps used on marine tanks; as I see it, on a freshwater I can use it to hide the heater system, keep the pH roughly stable by jamming it with mossballs, pull out some debris with a bunch of shrimps, breed up some food for the tank, chuck in a load of sintered glass blocks for an extra bacteria reservoir, possibly use it as a breeding tank, and use it as a nitrate sink. I can also use it to do PWC's if the substrate looks clean enough that it doesn't need hoovering, to avoid disturbing the showtank. The more I think about it, the more attractive it gets.

So, my questions.

1) I have absolutely no experience with doing anything on this scale; what sort of pump rates will I need for the tank?

2) When I put the filter in, should it go before or after the sump? I'm thinking after, since if I put it before it'll get way more clogged up and letting everything go through the sump first will remove a lot of the junk and extend the filter life?

3) Will an under-gravel filter be good enough to accomodate a 150-200 gal tank?

4) Will a 15 gal sump be enough, or should I use it as my emergency tank and get something bigger for the sump?

5) Are there any species of moss which hang from ledges? I'd quite like the inflow into the main tank to disturb a curtain of moss.

6) As far as spotlighting goes; are there any products which, say, filter the light through a rotating disk with holes drilled in to create a moving dappled effect? Or will I need to make my own!

7) The backing will be sculpted from polystyrene and cement; will this need to be sealed or treated in any way to make it safe?

8) Is there anything else I could use my sump for?

9) Any suggestions for another centrepiece fish or another tightly-shoaling small fish?

I'm bound to think up more questions as I go along. Thanks in advance!