What exactly are you looking to keep, SPS, LPS, softies?
Personally, I am leery of the cost savings LEDs represent. Given the high initial expense, it would take several years to see the return. Because the technology is in its relative infancy, I think further advancements are coming soon. Which means a lot of LED buyers will end up replacing units sooner than later, negating the cost saving.
Have you considered solar tubes? Depending on the tank's location and your willingness to drill holes in your roof or walls, it's definitely the cheapest option for someone in the sunbelt.