bio-balls, fuge query

[luvnpc69]

this is a two part question...help is much appreciated....

1) i have read that removing bio-balls from my wet-dry sump/filter may be necessary...how necessary is this and what is the reasoning?

2) i keep reading about large refugiums, up to 20 gallons or so...i have a 55 gallon tank with an approx. 10 gallon wet-dry...i mainly plan on keeping anemones, corals, crabs, shrimp, scallops, cucs and other inverts, but would also like a fish or three: probably a scooter blenny, clownfish, and eventually a mandarin....i have a 2.5 gallon fuge on the way...i will stock it with a couple pieces of live rock and some cheato, perhaps a mangrove or two... i have plenty of pods right now and will probably buy a bottle to help kickstart the fuge... do i need a substrate in the fuge?...will i be able to support my tank with this size fuge? why is it necessary to have such a large (20 gallon) fuge?
thanks