I would use a thin sheet of acrylic. It tends to transmit light a bit better with less absorption and attenuation. Yes, both glass and acrylic will attenuate light and absorb some spectra. You just have to pick the lesser of the evils. Either that, or try to reduce splashing or whatever is causing the splash to begin with. The latter is easier said than done, unfortunately.
I get some splash, myself, but I wipe it off weekly. A good oil-based cleaner for the reflectors can protect them from most of the splash (not all but most). I use Zep stainless steel cleaner. If you get it, be sure it is the non-abrasive kind.
