I saw an old thread and I needed to make people aware of the problems with spray foam insulation in the aquarium.
DO NOT USE "great stuff" spray foam in any environment where living things will constantly be exposed to it. It contains isocynate a molecule similar to cyanide which means I could break down into cyanide. It contains hydro fluorocarbon which break down into water soluble extremely corrosive acids. It contains polyol if I remember right this is a polyurethane solvent which gases off (never stops releasing this gas into the air or in this case water). In houses with very limited air flow through it into the living space it is much diluted. In an aquarium being such a closed environment this is asking for trouble