One of my female swordtails died yesterday after a few weeks. Two others I bought from the same source also look like they're in trouble. One is rapidly wagging its whole body and periodically rubbing on plants. Both of them are breathing heavily and sitting on the bottom a lot. I changed my water, but and here are the stats Before: pH 6.2, Ammonia 0.25, Nitrites 0, Nitrate 5.0ppm. After: Ph 6.2, Ammonia 0.10, Nitrites 0, Nitrate 3.0ppm. I keep thinking, if only I could give them more air, because they are panting. Should I get a stone filter?