Electrically you could to it with relays, but the timer idea definately would not work. This is one of those DIY things where its is better, easier, cheaper and more safe
to buy the extra ballast.
On the other subject I have 6x55 over a hundred and my hygro (sunset) grows straight to the top. No stunting. I raised this subject a while ago concerning my rotala. In the end I decided it was how I was pruning and replanting instead of lights or ferts. James Hoftiezer
Hoftiezer.Net - Journals and Libraries
Tank Journal - Aquascape ( Latest / Archive )
Tank Journal - Parts and Construction ( Latest / Archive )