I'm working on a foam wall for my tank, but I'm having trouble spreading the epoxy because it's so thick. Is there a way to thin it out to make it easier to spread?

Not fast way - mix up a little batch at a time and use a cheap throw-away paint brush and dab it all over the foam and the surrounding LR, then sprinkle the sugar size sand on the wet epoxy. Work one area at a time then move on.

I did two coats and still missed some areas.

You can glue coral to the rock wall too

this is mine




yeah I know it's not a Nano

Depending on the epoxy, try a hairdryer blowing on it while you brush it on. Some epoxies will thin out quite a bit with heat applied to them.