Mine usually drop about a month or so after I notice the new one coming in fully. On the topic of donating it to a zoo or aquarium, don't unless you really trust the facility. As a former aquarium biologist for two top 10 aquariums, it sounds better than it is. Many of the biologists don't have the skills that half the people on this forum have. Yeah they have huge tanks per our standards, but that's about it. Foods tend to be what is cheapest (squid and cut bait fish) and unlike hobbyists the biologists are responsible for systems they may have been assigned and are not particularly passionate about. I keep ever fish in my systems because I have a passion for keeping that animal and I will do everything I can to make it healthy and happy through it's entire life. Why do you think that many of us keep our fish so happy and healthy that they regularly reproduce for us, and you rarely see rare species at aquariums, yet alone producing young at aquariums. I am not saying there aren't a few good biologists out there, but I have met many more good biologists that are teachers, lawyers, doctors, welders, restaurant owners, professional athletes, etc. Just because you send your animal to an aquarium, doesn't mean it will be taken care of any better than you can.