For a really large system I would think about a basic layout first, then fill in the specifics.
1) Out from tank.
2) Filtration
..a) Mechanical
..b) Chemical
..c) Biological
3) Pump- External to tank, perhaps an above-the-water type used for spas or pools if your system is that big.
4) Return to tank
5) Safety.
6) Extras: Things you can add to a sump.
Details to think about:
1) Out from tank:
Large enough to carry large water flow.
Screened to minimize fish entry
Bottom of tank pickup to get the most debris
Other.
(What happens in case of power out?)
2a) Coarsest sponge, or even a grid such as a plastic 1/4" mesh.
A couple of coarsnesses of sponges: Coarse, medium, fine.
2b) Varies: Activated Carbon? Purigen? Peat Moss? Other?
2c) Nitrifying bacteria will live on the sponges, but a separate media may not be a bad idea. How about something like this:
http://www.drsfostersmith.com/product/p ... atid=15799
The coarsest of these could actually be used first, ahead of the mechanical media, especially if this is an open sump style and this media can be set up right under the line from the tank as a wet-dry material. It is very easy to clean of any coarse debris (plant leaves and similar material) and allows finer debris to flow through so the bacteria are not smothered.
also 2c) live plants? Great Bio-filter!
3) Sized for the system you want, isolated with shut off valves, unions and flapper style one way fittings so you can service it without flooding the filter room, and power out does not result in water flowing backwards, out of the tank, past the pump and into the sump to overflow. Not oil cooled. Many pumps can be controlled with a valve and choked down by 25% without a problem. Shutting down the flow more than that may cause problems with some pumps.
4) Spray bar, several point source returns. Does the water in/water out flow pattern result in a good overall water movement, and good cleaning of tight spots so debris does not build up? You can add more plumbing to direct a little water flow into these dead spots...
5) Follow what happens to the water in a 'power out' situation. Will it stay in the tank? Will the sump overflow? Does the pump need priming to re-start? Lots of research as you are designing the system. Lots of "What happens if...?"
GFI outlets.
Drain in the floor of the filter room.
Sink, water supply.
6) Heater, Auto fill, Auto dosing for plants, CO2, Monitors for all sorts of water chemistry, other. More research here, too. See number 5.
