Nikki, I would continue with the treatment and WC for a bit longer but maybe dose less of the medication.
Now I have something else to consider, someone in Canada wrote to me that has been following this thread and said that he has never had a clam in his tank, and has been up and running for over a year. One of his friends has several clams that he has had for about 6 months now and all have been doing great. They have there monthly meeting at this person home so he has had the opportunity to observe these clams. This friend of his gave him one of the clams and after be introduced it to his tank, ( clam free) about a week later that clam developed pinched mantle. Now I have been racking my little brain, wondering what the deal is, so talked with the lab again and conveyed this story to them. They said that there are different types of protozoan and it may be carried by some other marine animal but then attaches clams. If this is the case, then maybe that explains why we very seldom get clams that develop PM because we have nothing in our clam holding tanks except clams. All of our SPS are housed in a separate system all together. The clams that we did get in (croceas) that developed PM were at a wholesalers that house a lot of different marine animals in the same system. It seems to me that there are too many variables to consider when it comes to finding the source. We may never know where the protozoan comes from as there is just so much to consider. Just when I think that I may have figured it out then I hear stories like the one above.
Again, guess this is just another good reason to quarantine everything we introduce to our systems. But then again, do we medicate everything before we place livestock in the display tank? Will we ever know what could be the carrier and then passed onto the clams? Let’s face it, we all take a chance when we place anything into our systems.
We just don’t have thousands of dollars to invest in research! Maybe Mike can loan us the money for more research. LOL