What's the cheapest source for these bulbs? First time I'll be trying the Giesseman bulbs, have heard great things about them. Will be interesting to compare them with the excellent T8 bulbs I've used.
Have a look at Aquarium Specialty also. I bought from them a few months ago and it seemed like their pricing for bulbs and shipping was the best I could find. Of course that could have changed by now. Another plus was they were packaged very well and arrived quickly.