You will get a slightly glossy effect when you paint the outside because of the light reflecting off the glass. I have never heard that about silicon and oil based paints. Most paints used in boat building are oil based and they frequently use silicon together. I don't think it is possible to get rid of the reflecting aspect unless you get a completely different aquarium and use glass with a non-reflecting coat. I personally do not like painting the insides of a tank because, no matter how careful you are, you will sooner or later scratch the paint which will create a surface for algae to grow on. It seems to me that if you want white you are looking for something to stay clean looking or to give depth so streaks of algae are probably not what you are looking for.
If you can't/don't want to use paint have you considered some kind of white insert? Perhaps very thin white acrylic? or a piece of vinyl?
If you can't/don't want to use paint have you considered some kind of white insert? Perhaps very thin white acrylic? or a piece of vinyl?
