mold on wood aquarium cover

[fkshiu]

Kill the mold first by using a toothbrush and scrubbing with a bleach/water mixture. Allow to completely dry. Then use an acrylic wood sealer to prevent further mold growth. I've used sealer products by both Zinsser and Killz to good effect in my hood and stand.

[Soup]

Thank you for the info, very much appreciated. I just didn't want to use anything with anti-mildew that would leech in.

[schroeder]

If you don't use the Zinser specifically, you can use any outdoor grade product. Any kind of deck sealer should work. They all have UV resistance, and contain moldicide and fungiside.
I don't think it should be a problem if your hood is ventilated, but you may want to wait long enough for the canopy to completely dry (days as opposed to hours) for the volatiles to dissipate.