puks,
Like Dmorty217 has said, triggers are curious by nature. That right there is fact, which you say you want.
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I have gone scuba diving many times and many times seen triggers nip at things for the sake of it. They are curious by nature and biting is what they do. I can show you trigger bite marks on my wetsuit and flippers if you really want.
Please keep in mind that even if anyone here has not personally kept the bluethroat trigger, all of us have read the same fish profiles and articles on reef builders (amongst other places) over the years. We're doing our reading. We're seeing many people who keep saying the same things. When you read the same thing a million times from different sources, it more or less means that what we're reading is factual, not opinion. As animal keepers, our goal is to ensure the health and well-being of all animals. All we can do is answer a person's questions and explain our answers. After that, the person posing the question can ask follow-up questions or accept an answer. Your question has been answered by multiple people. Accept it or ask another question.