I would have thought the air in Qatar would be fairly dry most of the time, and even if not, the temps are such condensation should be minimal. Here in Queensland, which is humid, and cools down more at night, I still don't have any trouble with growth or condensation, and I never have full tanks, and yet hardly ever get even a teaspoonful of water in my separator filter. However my tanks do drain from the bottom, not via a pickup some distance off the bottom. So in a way I'm removing any crud as soon as it forms. That said, it is minimal as my filters last years - literally. I think you are worrying unnecessarily, but as usual, best thing is ask the locals, even if your Arabic is basic, most who would own a boat there would speak English.