Re: Tokis
Fish are very highly tuned to chemical cues in thier food. Basically, this means that a fish will not eat things that are naturally bad for it. Now, assuming the orange does not have any chemicals in it that a fish cannot detect, no fish will eat it if it will make it sick. I guess the moral of that story is to purchase organic non-pesticide fruit if you are really worried about it -- <shrug> I don't.
Let me give you an example: The higher levels of oxalic acid in Crytocoryne leaves do make them mildly toxic, consequently fish and snails do not consume it until it is soft and translucent and all the toxins have diffused away. Similarly for other oxalic acid containing plants, like spinach. My fish usually are not interested in spinach till its been in the tank a day or so. Sometimes they are not interested in fresh fruit or vegetables at all. But, I almost always give them a slice of whatever fresh produce I purchase... if they like it, good, if not, fine.