All of those puffers look like GSPs to me. Why do you think those ceramic rings contain bacteria? You must not add a puffer until your tank is completely cycled. You could add Safestart to the tank at the same time as the puffer to instant-cycle the tank. After the puffer is comfortable in there, you can start raising the SG .002/week. Have you added any decor in there?
See here to find out how high you need to go with the salt & more info on the care of a GSP:
http://www.thepufferforum.com/forum...cus/an-introduction-to-green-spotted-puffers/