When I do 100% water changes I always cup my bettas. Now, since I've owned bettas, I've always put them in the plastic cups that Hillshire Farm meat comes in (after I've washed it). I never really thought about it until now, but I do wash those cups with soap and water. I let them air dry, and use them for a variety of things, but also to cup my bettas. Could the soap be harmful to my boys? They're only in there for about 5 minutes tops, and always with some of the water from the tank. If it is harmful, what else can I do? I don't want to do anything other than cupping when doing water changes.