Lighting for tank change.
 

I might pick up 65g<36x18x24>? from a buddy to sit in place of my 40b, currently lit by 6 bulb t5ho.

tank is mixed reef with a current lean towards sps. will my current light cut the mustard or is this <freeish> upgrade going to cost me new lights?

what fixture is it? you will be ok if its a tek at least or a nova extreme pro

yup.. nova pro..

I wouldn't worry about it. should be fine over a 65. if you see any problems with some acros you set low, just move them up

Agreed. Should be enough light as long as flow and water conditions are excellent.