How can I convert a wet/dry to a Fuge?

[20yrs90gal]

convert an old wet/dry to a refuge??

Attached is a basic diagram of the factory configuration (attached in doc and xls) - - I hope it's legible.

I was thinking I could just remove bioballs, put in some live rock and cheata (SP) and clip on a grow light. But, not so sure about some things:

Questions:
Do I need Sand in refugium?
How should and will I reflow water?
How much water flow should I have, I guess I'm turning about 700 - 800 GPH with the setup I have now- is that too much?

Any comments recommendations would be appreciated!

FYI: problems - way too much nitrates from infrequent water changes (I know. . . I know - but I travel way too much). Fish are happy, coral not so much:(.

90gal
4 VHO 4' 110W (2 white, 2 blue) - 8 -10 hrs/day
auto top off refill
350w stainless heater
Blueline 1200 gph external pump - from wet/dry
skimmer with rio pump
CPR overflow - 1" drain (800 GPH)
external filter - magnum 350 (running carbon)
Using Phosguard and Purigen in wet/dry

[Cristi]

You do not need sand in the refugium. I would just put some LR rubble and some cheato in that chamber where you have the bioballs. Most recommendations I have read are to gradually remove the bioballs. The only thing you will need to do is increase the water level in the back since you will need the cheato to be completely submersed.

[20yrs90gal]

THanks Cristi,

Do you know if a 13w florescant bulb will be good? I have found a work light with a plastic cover that would be pretty good for hanging above the fuge. Couldn't find any "grow" lights at Lowes or Wal-Mart that would work in a clip light. So I just went with a standard bulb.
Thoughts?

Oh, BTW I already pulled out all the bio balls this am. I have enough live rock in the tank I should be OK (I hope!!!!)