If you use an epoxy mixture with colloidal silica filler and use that to bond the baffles in place and form fillets around it on both sides, it is strong enough so you don't need fabric
. Make sure you sand the surfaces to be bonded and the surfaces where the fillets go with 80-grit paper. Vacuum all dust out and wipe with acetone before bonding.
But you will need to paint
. Like Rick wrote, there are special paints for it but I can't help you with that. I once searched for a "taste-free" and food-safe paint and came up with the standard Awlgrip. That stuff is poison in the can but completely inert once cured. But it probably is too expensive and too much work for the insides of a water tank! Probably a single
is good too but you will have to ask the manufacturers. Some white paints still have lead in it so be careful.