So I've had my tank set up for about 6 weeks. (And had filters & media in my previous tank for another 6 weeks prior to that) I did an in fish cycle, a few cherry barbs and a few cory, lost a few but after about three weeks, nobody died, my levels started to drop and finally hit 0,0,0... On week 3 I added two gourami's & two cory's (dwarf & opaline) My ammonia level's did a tiny spike to .50 and Nitrate stayed at 0, I did my water changes, and they went back to 0 again and stayed that way. On week 4 I added about 7 fish. (a few cory's and two cherry barbs to complete my school because two had died), did the same as previous week, but went back down to 0,0,0. Week 5, I added 5 fish (a school of longtail zebra danio's) small spike, and after 1 day, and a water change dropped to normal. Week 6 (this week) I added 4 more corydoras, and my ammonia levels shot through the roof, and for the past three days no matter what I do I can't get them to stay down. Even my Nitrate's are up a bit. I've lost two catfish in two days, and my ammonia is crazy, between 3.0 and 4.0. Last night I did a 50% water change, used regular water conditioner, and ammo-lock (two tablets). I did turn my filters off during the water change (off for about 15-20 minutes max) and I'm wondering if this may have disrupt my cycle? Today I did a 25% water change, no ammo-lock this time, filters off again. Am I completely disrupting my cycle by turning my filter off? What the heck am I doing wrong? I don't think my tank is over stocked, seeing as I even moved some fish into my other tanks just in case. 40g breeder tank 6 cherry barbs 5 platy (females) 2 gourami (dwarf & opaline) 16 corydoras (panda's, Agassiz, albino & emerald) I had 5 longfin zebra danio's but moved them into my other tank as well as my only male platy. Any insight would be helpful!!!