Haven't had that problem Jamie, but then again I don't have many SPS. I had a slight issue with a my large cleaner shrimp and peps. These were bigger peps too. The cleaner goes after them if they get to close. I put six large peps in my 75 about a month or so ago, and now I have only been able to count 2 at night. Not sure if the cleaner is the culprit. But, they worked wonders on the aptasia. No aptasia at all now. I don't think you need to worry about the peps doing anything to the other shrimp. More so vice versa if anything. And if you can score peps from port aransas, that would be your best bet. I have heard people having hit or miss situations with other peps from stores/online etc. But have heard mostly positive results with the port A peps.