Water is roughly 8lbs per gallon. So you have 320 lbs in water plus your tank and whatever the fish weigh. I'm not an engineer but it would seem your at 1/2 the shelfs capacity. Which means you should be safe! I'm really big on only using 75% capacity at max.
So your at a solid 400lbs easily I'd still call it 500 to be safe. (I always over estimate, that way no surprises)I would keep it on a lower shelf but it still sounds fine. It would seem the unit would be rated at 1000 lbs not the shelf but either way it appears your safe.
I'm not sure I would keep an aquarium directly on wire shelving without a solid base. If the wire flexes it could cause cracks in the glass. There is a reason that every aquarium stand you see has a flat surface as the base.