Do you know if metronidazole is incompatible with solar filters (octocrylene).

There is little chance that such incompatibility is described in the literature. Now both Octocrylene and metronidazole have a special chemical structure and an interaction seems to me not ruled out.  

I found the following text  

In the end I suspect that first applying your metronidazole of choice (MetroGel, Rozex, MetroCream, metro lotion or noritate) followed by a low irritant physical sunscreen (eg. Linda Sy ZincO Cream, RosaceaCare Sunscreen 30 et. Al.) is going to offer rosacea sufferers a better chance of an elegant and well tolerated protection regime. would we not follow this recommendation? You can prepare the Metronidazole hydrophilic gel from the TMF.