Rocker,
(I'll phone you later!),
I'm assuming that you have a fibreglass reinforced sand filter?
Paint with a bit of epoxy to control the glass, then the epoxy will need some UV protection. It seems to be a little known fact that normal flowcoat (which is a brushable gel-coat and probably what was used originally) will adhere to epoxy, so you could use that in the original colour, or just a bit of house paint would do.
cheers,
P