I have a tank that has been established and cycled for about a year and a half. 3 weeks ago I added a few new fish, my ammonia spiked up to 2. I have been using fritz complete, and daily large (50%+ water changes) and have slowly brought the tank down to where the ammonia reading is most mornings when I test around .5, some days has crept back up to 1. I’m at my wits end, I’ve continued to dose with fritz complete, added a second fx6 filter to a tank that I thought was already over filtered, added ammonia pads to the existing and new filter, added additional bio media to each filter, vacuumed the substrate really good, skipped days of feeding and I can still not get the ammonia to test below 0.5. I’ve tested my tap water and that tests as 0 ammonia. My nitrites have remained at 0 and nitrates low for the entirety of this ordeal. What gives? And what else can I possibly do to get the ammonia back to 0?