Mike, Thank you for responding to my questions about the cories with "red spot". Unfortunately, I did not record the readings from the test run by the pet store. I will have it tested again and be sure to record the info. But, until then, they said everything was near perfect except that the water was very hard. I could not understand this because I was using bottled sodium free drinking water "as directed by a different pet store". They told me I didn't need to use the water conditioner since I would not be using tap water. I had better results using tap water and the conditioner to remove chlorine and provide slime until I started using the suggested procedures from pet stores! I have returned to my tried and true method of using tap water with instant chlorine remover and conditioner. No, I do not have a quarantine tank. My husband already thinks I have gone overboard with my only tank. Is is possible to use a 5 gal. for that purpose and only set it up when needed? Unfortunately, my sick cory met his demise that day. I was afraid to wait for someone to respond. I have never used this form of communication and really didn't know if anyone would actually answer me. The only thing that you didn't address (probably because I was missing some important info) was the amount of gravel I have in the tank. I may have my 36 gal. too crowded. I have 5 rummy nose tetras, two black neons, 4 neon tetras, 2 adult platys (about 11 babies survived that are in there too), 2 corries, 1 clown loach, 1 plec, 2 cherry barbs (I just lost 2), and I had 2 lamp eye tetras.