My 2 cents on the carbon issue is this. The 2 Oscars I have now one of them has HITH the other doesn't. I had for years not used carbon except for after treating a sickness, about a month ago I threw some in my AC110 and within a few weeks I noticed a small hole developing on one of my Oscars head. I've pulled the carbon and it's stopped growing. I check nitrites, nitrates, and for ammonia once a month with a liquid tube kit highest I've seen the ammonia is 0.25 ppm nitrites 5ppm nitrates 20ppm.