The only way I could see drop-eye being genetic is if in some wild populations it produced some advantage to survival. Do you see drop-eye in wild aros? I'm really not sure, all the wild aro's Ive seen haven't had it. While this is of course possible, it would take extensive testing to prove or disprove. The unfortunate thing is there are so few accessible hobbyists who breed aro's to get any information on whether it is an inherited trait. Personally, I'm not convinced it is genetic or induced by BB tanks. On the subject of bare tanks, IMO a bare tank will not induce the full range of behavior one would see in a wild aro. With no environment per se to interact with, it really won't use all of the features which it has evolved with which to do so. Like keeping a geophagus in a tank with large gravel, you really won't see any realistic representation of this animal in the wild. Plus, hunting won't be the stimulating activity it would be in the wild, where it has to use all of its intelligence to capture prey succesfully. Just my two cents