I did a quick water change today to fix my salt levels in my tank. 13.5 small tank. I used reef safe salt. However for about 1-3 cups of fresh clean water I purée directly into the tank not filter system. It hit my Arrowhead Crab. He backed up quickly but my concern is — will he be ok??? I put the rest of the water through filter system. I have no idea why I don’t fresh in the regular part of tank. Any comments to lessen my concern on my crab ?