One of the seven female red & black swordtails I acquired last Friday appears to have dropsy or something similar. Symptoms: slow to eat, unresponsive (I can pet it and it barely moves), swimming slowly at the top of the tank, not schooling with the other six, bloated stomach (or very pregnant), and pining out scales (although only in the underside of its stomach). Just changed 1/3 of the water (15 gallon tank) and added 1 tbsp of salt to the new stuff. PH is 7.6, ammonia 0ppm, nitrate 0ppm, nitrates 30ppm (weird since I change 1/3 of the water three times a week and have tons of hornwort). Total stock is 7 female swordtails, 5 paleatus Corys, and 1 aeneus Cory. Any thoughts?
. Hopefully the others don't get whatever it is.