I have a Zebra barred dartfish which I've had for a few months. About 4 weeks ago this active swimmer stopped coming out and began hiding more, but would still eat. I added a sea cucumber to the tank a few days after that, which apparently was not happy in my tank. I lost my six line wrasse and my algae blenny within 48 hours and returned the cucumber to LFS. My engineer goby and clown fish perked up soon after adding some carbon to the water, but the dartfish wouldn't come out to eat. I moved him to quarentine and let him swim there for a while. He still wouldn't eat after a few days, had clamped fins, and seemed to have trouble swimming. His condition has gotten worse, as now he will not swim at all, will not eat, and occasionlly blows a clear bubble then sucks it back in his mouth. He still has good coloration and no visible signs of disease. Does anyone know what might be wrong with him?