1) Tropical.......greater than 76
Temperate.....between.....65 to 75
Cold Less than 65
That's just my opinion though.....temperate and cold are used interchangeably it seems.... probably since so few colder hobbiest tanks are out there.
2) Feeding consists of mysis, plankton that I collect, scallops, clams, cyclopeeze, oyster eggs, and brine.
3) Tidepool....shallow tank kept at 55 F or below. Cold critters are very hardy except for anemones which don't like nitates above 15ppm. These tanks really have few requirements beyond temp.
4) Water flows from tank to sump....there are some bioballs in the overflow.....a skimmer is in the sump....one return pump returns water from the sump to the tank via the chiller. I have a single Tunze pump in each tank for circulation.....that's it. Oh, I recently hooked up a sulfer denitrator to help with nitrate control.