brackish to fowlr?

i have a 75 gal brackish and bought all my fish with the intention of swithching to marine slowly. anyways im at 1.012 sg a ph of 7.7. my question is do i need an ro/di filter for a fowlr tank?

anyone out there done this before?? if so how will my scats monos and gymnothorax tile eels mix with marine invertabrates?
pfh

thanks for the advice brackeeper i had no luck finding info on bracs gone marine out there. so many sources recommend certain brack species to go full marine but i havent seen any info or even pics of scats in reefs.

and wayne its not that i wanted to mix bracks and marines it just seemed to make sense that if they move to marine in nature as they age i could mix them. but really i wanted the live rock filtration and cleaning crew more than triggers or clowns. maybe a coral of some sort

as for the ro/di water is it a good idea in a high end brack tank. my fish are healthy using treated water, can marine fish live in treated tap water? ( i have good quality tap water in my city)

thanks again

i have five pounds of crushed coral. a few pounds of a blue sand my lfs gave me. and some gravel from another tank i used to start my cycle long ago. my tap water is 7.0 and stubborn. i dont have any driftwood which lowers ph. maybe i just need more cc?
been struggling to raise slowly.
any suggestions?

just curious what exactly was the problem with the coral. puffers chewing em?