The FX 6 uses about 45 watts, 24 hours a day, 31 days/month that would be 33.5kwh. Assuming you're in the US it looks like the average electricity price is $.12/kwh. So about $4/month.
An air pump only uses a few watts. Let's say 5, that's about $.45 cents worth of electricity.
If you wanted to try and run the FX6 with solar panels you'd probably need at least one big deep cycle battery , Maybe 300 watts of panels to make sure you can survive rainy days, a good charge controller and sine wave inverter. Probably looking at optimistically $500+ if you include mounting parts for the panels outside. That's a payback period of 10 years.
You'll likely need to replace the battery at least once over that period, so probably more like 15. And that's optimistic.