ReefkprZ gave me the same recipe for my dwarf seahorse tank
Anialated the little fiends. ReefkprZ also suggested if you want to really make sure you nailed the little pest, take the rock out and place in some tank water. Give you choice of treatment, wait for 45 minutes...check to see if the little guy reappears. Do a second treament just to make sure. Make sure to keep track of the water levels in the container if you use lemon juice or strong kalkwasser'
Also check your levels in you DS, especially Salinity, nitra, nirto, ammonia. Pests like these love salinities over 1.026, and especially tastey waste snacks. Check for dead spots in your tank. I'd do a 20% water change. Pest like aiptasia lay dormant waiting for the perfect water levels to spawn and thrive. I found this out the hard way in my seahorse tanks.
Let Us know how the war is doing. Good luck General