Gluing rocks: can hardware store spray foam do the trick?

[Littorina]

Hi everyone!

     Started aquascaping my marco rock for my new 28 gallon build.  I began gluing my rockwork together with the Fluval Sea marine epoxy, but I ran out last night, and still have 2 pieces of rock to do! 

Won't have a vehicle today to go get more at a LFS, so I was debating about using "Great Stuff" insulation foam from Home Depot.....I know many of you have been using it to make "faux" rocks and faux rock walls, but I just want to glue a few pieces of marco rocks together

I've been googling the subject, and reading various results.  Wonder if anyone here has any advice or experience?

Questions:

1) does the foam hold up long term under UV light? (I will be using a Maxspec Razor 120w LED)

2) does it eventually breakdown in the water?

Should I wait and get the marine epoxy (which was holding really well, even when still soft!), or try some spray foam? 

Thanks!

[Stussi613]

The black landscaping one is uv resistant, but if you're just using it to stick rock together it shouldn't matter.  If any if it is visible you'll need to coat it with epoxy to keep fish from picking at it...and while you're at it you might as well put sand on the epoxy to get rid of the black colour of the foam.   

Or just get more epoxy to stick the rocks together.

[Littorina]

Yep, sounds like I'd be needing epoxy regardless.  And I was very impressed with how strong the epoxy became overnight, great product, so I'll just wait and get more, instead of going for the foam.....