I changed out 6 gallons in a 30 gallon plus I changed out 6 gallons early this morning also so that makes 12 gallons in all today, then I added 3 tetracycline tablets just a few minutes ago, The brand name of these are Mardel the same company that makes maracyn so I figured it would be ok to just change out some water and add the tetracycline where the company made both the products. The fish are starting to hang out at the top of the tank. I was going to let you all know the water readings. The ammonia is 0 the nitrites are 0 also the ph is 7.2 I have a test kit for the gh and kh also, I just have to test them,. I will do this soon after I get back with the camera..I am going after it now..