Kei,
I always put my bettas in smaller bowls when treating them with the bettafix. I only have to use 6-12 drops depending on what size bowl/cup I use. I find that a 2 pint container is usually sufficient. Large enough so that I can syphon out the dirts and still leave enough water in to last the 7 day treatment. Floating the bowl in a heated tank also helps to keep the temps where they need to be.
Emg <img src="/images/graemlins/cool.gif" alt="" />