Hey guys. When I introduced the CO2 in my tank my ph shifted abruptly, causing my betta to get fin rot. I wasn't sure for the longest time if he was really sick because the tips of his fins are naturally black, so by the time I noticed it was already pretty serious, and then got worse really really fast. No salt, pristine water or organic meds. I'm past that point and he's in critical condition. I've been doing large daily water changes and very meticulous gravel vacs. Its doing nothing for him and big gashes of his tail are missing and a few pieces look like they'll be ready to fall off any minute now. I need to go today before the stores close to purchase some medicine for him. I usually try to be patient and wait for people on this forum to give me some guidance before doing any big changes or moves on my tank, but I seriously cant wait another day. I would hope some of these meds don't mess with my cycle too much. So far people have mentioned furan-2, tertacycline and the maracyn combo. Please please i really need advice! I'm getting ready to go to the lfs and will probably purchase the furan2 if i get no reply before then. I'll be checking my phone every five minutes till then lol. Thanks everyone.