I have a 75 gallon tank that we got a week ago. This is our second 75 gallon tank last one we had for 2 years before we sold it. Anyway... water gh is 40-80 kh is 20 ph reads at 6.5 n02 .5 n03 .2. And we have 2 baby jack dempesys. 5 mollies a rope fish spiney eel sun cat and a ralph cat and 30 baby guppies to feed the eel and jacks. Mollies are at the bottom gasping jacks are at the top. And eel is sticking his head out of the sand gasping. What can I do necer had this problem with our other tank.