From the submissions page at Hippocampus Magazine:
Just because we pass on a particular submission does not mean it does not have merit; we publish 8-12 pieces per issue, and this often means turning away strong work. Sometimes it’s as simple as an essay with similar theme or style was recently published. Do not take editorial decisions personally. Just sitting down and getting your thoughts on paper is a task for which you should feel great pride—not everyone can do it. Every piece of writing has value. We feel it is important to spread the message of being persistent and diligent in your search for publication. Never let rejection discourage you from sharing your story. Just because it is not right for us or right for us at this time does not mean it will not find a more fitting or timely home. Write on.