Hahaha, Kai, I wouldn't have thought to see how old the thread was either (admins, can we do something to keep stale threads from becoming active again?)
We feed the whole processed tilapia, dorsal fin and all. Liesl has never had a problem with it. It is sharp but she loves to crunch up the fins. Scales, head, etc., all contain valuable nutrients and calcium. This is not to say that it would be impossible for a dorsal fin spike to cause a problem, but I personally don't worry too much about it.
Liesl, b. 1/1/11