OK,
You have:
2 * 250 W = 500 W Metal Halide
2 * 56 W = 112 W T-5
Total lights = 612 W.
I'll assume a 12 hr light period.
12 * 612 = 7344 W-hrs.
You also have:
180 W pump
18 W UV light
198 W of power that always in use. (Note: I suspect that the 180W rating on your pump is a maximum rating, and the pump may not actually be using that much power, but I have no idea what its really using, so I'll just use the number you gave.)
24 hrs * 198 W = 4752 W-hrs.
total power used per day = 7344 + 4752 = 12096 W-hrs.
1 kW = 1000W.
total power used per day = 12.1 kW-hrs.
30.5 days per month.
30.5 * 12.1 = 368.2 kW-hrs per month.
Someone said that Long Island has an electric rate of $0.18 per kW-hr.
So total electric is:
.18 * 368.2 = $66.27
As for solar panels, the cheapest thing is probably to try and use something like the solatubes and bring use natural sunlight to light the tank instead of trying to convert sunlight into electricity and then back into light. I think you'll find that a 500W solar panel is rather expensive.
Also, all of the electricity that you use on your tank will eventually be turned into heat. However, where I live, my electricity runs around $0.09 per kW-hr, and my natural gas run around $0.04 per kW-hr. The reason why we heat our homes with something other then electricity is because the other energy is much cheaper at producing heat. This relationship is preatty much fixed by the second law of thermodynamics.