Vivarium trouble, non toxic sealant?

[axolotlfreak56]

I've looked and looked and looked and I have no idea what to use. I'm not even sure if I need a sealant. Basically, the way its setup is that I sculpted the styrofoam and grouted it and painted it with non toxic acrylic paint. Everything is 100% dry. However with the water cycling through, going through the waterfalls the water becomes a brown murky color. I'm assuming its the grout because the paint isn't coming off. That said, I have no idea what to do. The grout is definitely toxic. I know the problem, but I can't figure out the solution. Every sealer I've found is toxic and I have no idea what to do...

 

[Greatwtehunter]

Are you positive it's the grout? If you've painted over all of it with the acyrlic paint then I would assume that would keep the water from interacting with the grout. Is your water touching the substrate or maybe some wood at all? Do you have a pic of the setup handy?