I saw a diagram using pvc to hold plastic diffuser for florescent lamps 1"
above the bottom and fiberglass screen for a separation then 1" of coarse
sand, screen again then 2" of fine and live sands. Live rock and protein
skimmer that should work. Would I need light on the live rock in the sump?

thats mostly correct as with any sand bed it will in time become live, so "then 2" of fine
and live sands" live or not doesnt really make a difference, what does make the biggest
difference is did you do it all correctly, if you mess up with it it can turn into a major
pain, including dead fish/corals and a stinky house. by messing up some is in the design &
construction, others are in thinking you know how it works and trying to make it better.
ive done both DSB's and plennums, plennums are much better at nitrate removal than any
dsb, but there harder to build, and take a better knowledge of the system before you
start.

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richard reynolds