Why is obvious, but not near as much fun as monkeying around inside them. Besides cutting ourselves, the chance of introducing possible pollution is too great. For these reasons, most activity calling for submergence can be accomplished with tongs, a probe or siphon device engineered for aquarium use. Real manual dexterity without contaminants and protection from infection is attained with long rubber gloves. Use a net as a partition when dealing with stingerees like lionfishes and their relatives, and biters such as triggerfishes.
All wounds are potentially serious, and require critical evaluation.
If you have a known allergen reaction to proteinaceous stings on land, check with your doctor concerning aquatic possibilities and treatment. If you use gloves or keep your mitts out of the system as proscribed, or carefully touch these animals on calloused hands only, promptly cleaning up after handling, you might never know their peculiar, sticky, ensuing pain. This is no joke. Avoid contact with these invertebrates and whatever touches them . Those stinging cells attach to aquarium sides, decor and in-tank tools, and can still sting hours later.