You won't be able to beat 10-34-0 or 11-37-0 liquid for economy, I'd be willing to bet. However, you do have the expense of the equipment to distribute it. When fertilizing lakes that large, I use a 100 gallon tank and small bilge pump to distribute undiluted fertilizer into the propwash of my boat. It works great. Handling quantities of liquid fertilizer can be problematic, however.

You could call Southern Excellence and see about shipping a pallet or two of their product to you. It's really easy to use.

The wettable powder type fertilizers are great too. Higher phosporous means lower application rates than with liquid, so the cost differential is reduced. It can be shipped too. I use Trophy Maker but I can't remember the name of the manufacturer off the top of my head.

I don't know anything about fertilizing in California, but I don't see why recommendations for southern states wouldn't apply. Wait 'til your water is a bit warmer and don't fertilize if aquatic weeds are a problem.