I guess it depends how brave you are. Based on the standard glass thickness calculations, regular 19mm glass on a 10x4x4' tank has a safety factor of 1.2, so barely over the minimum thickness required to support that sort of weight. If the glass is toughened the strength increased by a factor of about 5, so you'd be plenty safe. Personally, the idea of having nothing but silicone holding together a tank of that size puts the s**ts up me, if it were me I'd be going for steel framing.
There's more then just 5 pieces of glass there's probably around 21 or so in the top and bottom you do not see. Also I would only do it on a solid steal frame. I've never had a problem as long as its done right. I would only do it on a solid steal stand as well. Ive seen many tanks done like this and I've done many that been up for almost ten years. I've never had a problem or seen a problem as long as its done right, and stand is reinforced right. Flexing and settling would be my main concern.
Steel framing is only going to help. It's an awesome Idea if you can do it I agree. On these builds I didn't need to. I have a 7 ft by 8 ft 30 plus because of span there's aluminum bracing. I'll get some pics when I find them.
