Non-toxic paint sealer for background?

[rhino5]

I am building a background using styrofoam board. I plan on painting it with deatail and texture, and need to find a clear paint to seal the whole thing. The base will be sitting in the substrate, and there is a water feature so it needs to hold up to moisture, and be non-toxic to the frogs. Has anyone delt with this, any suggestions?

[schlegelbagel]

you need to use an epoxy sealent with a water feature.