My fish have been dying suddenly and without any visable signs. Things started going downhill when I purchased a discus form the local petshop. My tank got ick and i treated it with salt. Then about a week later, things went down hill. I woke this morning to find two of my clown loaches dead, one floating and one on the bottom. To make things worse a tiger barb was dead but i noticed him looking rough after yesterdays water change. I checked my all my nitrates, ph and amonia. Which is ph of 0ppm, amonia 0ppm, NO2 0ppm, NO3 5-10ppm. I just increased my filtration with an eheim 2217 that i got today, I have a airstone and do 30 percent water changes everyday. I have had 3 clown loaches, 2 blue rams and 3 tiger barbs die within the last week or so. Currently I have the 2 discus, one silver dat, 4 clown loaches and 2 tiger barbs. I dont know whats wrong and if anyone has any ideas that would be cool.