So yesterday I did a water change and cleaned 1 of my 2 canisters. This morning both of my 4 inch thinbars were breathing heavy and disoriented. All of my other fish were fine. I have heard they are sensitive when they are young, but not sure what I'm doing wrong. Well one has died this afternoon and the other still looks weak. My nitrates were between 10 and 20. I notice a lot after water changes even my big datnoid breathes heavy and gulps at the surface. Can anyone shed some light on what is going on?