38g Paludarium build styrofoam need help

[shibbyplustax]

im going to build my first paludarium / vivarium. iv had a vivarium for a few months now in a 20h tank but used a t-rex foam rainforest rapids insert. i am building this new 38 gallon viv because my 20h tank has a crack in the top of it and decided to go bigger and build my own.

i started cutting out the styrofoam into the shapes i wanted and just placed them together in the tank in order to get a feel of how it would fit. the pain in the butt part is that each peice of styrofoam, once it is sealed and painted, will have to be put together inside of the tank becuase tthe plastic divider in the middle of the tank wont allow me to build it outside and simply place it inside. i am currently stuck at this part as i cant do anything until the peices are sealed and painted. i am having trouble finding a sealant that will meet my requirments. if anyone can let me know of a product that meets these following requirments i would greatly appreciate it and can get started on finishing this project and continue posting its progress.

I need a sealant that will do the following:
-first off needs to be reptile/ fish safe
-i want it to dry up pretty hard in order to make the styrofoam alittle more durable / easier cleanup
-i want to be able to paint on the outside of it in order to make the details look more realistic
-moderatly easy to work with

I also would like to know of paints that are aquarium/ reptile safe and long lasting/ durable

any help on this would be greatly appreciated as i cant got any farther in my project until this gets done. i am not going to get into the mechanics or plumbing of this project just yet as it will be hard to describe without pictures. once again ill keep everyone posted on the status of this build just so long as i can get some input on how to get past this step

[JoeG]

The most common method you see is cement grout, and there are several threads on how to do it, including safe paints. You can also use UGL DryLok which goes on like paint and can be colored using cement coloring agents. Its a lot easier, but you have to add the rock detail to the foam more so than if you use cement grout which often looks more like natural rock on its own. Both approaches are aquarium safe, I find more aquarium sites discuss/use the drylok method.

[Averhoeven]

I used a layer of Activa Permastone (hobby shop plaster polymer discussed in other threads here as a substitute for habicrete. Then I put a layer or 2 of drylock over it. Works great, looks like rock.

To make it stand immersed conditions I would act a coat of epoxy or silcone with perhaps a layer of acrylic (minwax polycrylic works) between for added water resistance.