If you are adding enough LR
, then that will be all the filtration you need for the tank put like 10 lbs in the sump and 10 lbs in the main tank or more and you're set.
As for the water, the jugs of distilled are ok, but don't use tap whatever you do. You have no way of knowing what chemicals are in the tapwater that could harm inverts or promote nuisance algae growth. Unless you buy the RO
unit you can't be sure you've removed all the crap. Look for the water machines that you see outside grocery stores or sometimes inside. These machines usually dispense reverse osmosis filtered water that is fine for use in reef tanks. Just check the labelling to see what the filtration method is before using it. You can find reverse osmosis units on just about every aquarium supply website or even on e-bay.