Had three oto's, one for over a year, two for over 6 months. One passed away last week. Both remaining are not moving around, my oldest is sitting on the thermometer with clamped fins the other is sticking near by, very pale and not searching for food. They won't budge unless i make them. Got a few new guys a few days ago and they have all dropped dead, literally from the walls and although they were part of a new shipment (i know, bad idea) I've never had new oto's just die like that especially not all of them. Just saw one fall off the wall and die within a min. Really worried about these last two especially because I really like these guys. 0 ammonia, 0 nitrites, under 10ppm I've been checking right before my weekly water changes every friday for the past three weeks. Just changed the filter cartridge because the water was starting to smell fishy and it's been over 6 weeks.