Hi, we got an established tank through Facebook market, got it cleaned up and running, and have noticed these but figured they wouldn't make it through all the changes. However, these little dudes have managed to open and close since we got them a few weeks ago. But I don't know what they are. They are white with a slightly orange-ish middle. You can't see them well in the photos because of my light, but I figured you guys might be able to identify them.