Yeah I will go back to the store tomorrow, pay for the fish and just ask that they could treat it there at the store.
I think I will remove the GG into a big plastic tub, set up a heater and filter and keep him in there for a few days isolated, move around the decorations. so I allow the festae to settle in and establish a territory before I reintroduce the gourami. cause the gourami right now has no competition and I don't want to risk him just attacking the festae.