Answer: Without seeing the beetle, I can't identify it with certainty, but it sounds like a fungus beetle. These fellas shouldn't hurt your flowers or the potting soil in your containers. You might be surprised how many insects are considered beneficial in the garden. For a positive identification you might want to collect a few in a sealable plastic baggie and take them to your nursery or local Cooperative Extension office. Once you know for sure what you're dealing with you can make informed decisions about whether or not you need to control them.
Best wishes with your container garden!
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