The bulb has this written on it: F20T12.D.ECO Daylight 20W. So I'm guessing that it stands for T-12?
I went to Home Depot to look at the lights being offered. It was close by. They don't have an extensive selection. Neither did Lowes. I asked about the 6500 lumens concept. The highest rated lumens they had for 24" bulbs was 2350. They did have 6500 Kelvin on one of them and that was explained to be as being part of the color spectrum, from white to blue, with 6500 being the highest end, with the blue. I'm not not sure if the 6500 lumens I was asking about was the same thing as 6500 K, or coincidental, or whether it would be adequate indoor lighting for the sundews. Also, isn't there a difference between what we perceive as brightness and what is most beneficial for the plants?
And yes, I have considered going to a tropical fish store, for that purpose. I want to replace 10 bulbs. I'm thinking that a pet shop might be more expensive.