I have a 75-gal
tank that cycled in November 2020. Since then I added 18 fish (10 and then in 3 weeks 8 more). In the beginning of January, I decided to clean my Cascade 1000 canister filter because I read you need to clean it once a month. I cleaned floss and rough sponge in the aquarium water and I left bio media alone (I didn't clean it at all) thinking that BB is primarily in the bio media. Somehow this has restarted my cycle! It's been more than a week now and my ammonia keeps on rising (it's a awful 8.0 now) and nitrite is 0.0, nitrate is 5.0. Ph is 7.4. I change 50% of water every day for the past week. I added "one and only" BB, zeolite to the filter, nothing helps. I lost my guppies and pleco. Tetras and mollies are hanging on because of AmmoLock. My question is: where did all BB go? It looks like it got completely wiped out. I am now afraid to touch the filter. I know I will have to eventually clean it again, but I don't want to repeat the same mistake again. Should I not clean it every month while the tank is still establishing (the first 4-5 months)? Also, should I vacuum the gravel while it's now cycling with fish-in? I am afraid that I will disturb BB in the gravel if I vacuum. And also should I keep on doing 50% water changes every day untill ammonia goes down? I lady at a local fish store (not a chain-store) told me not to change water for the next 3 weeks while it's cycling. I can't see how my fish can survive that.
And it's nerve-racking to have a fish-in cycling. I have nightmares about all my fish dying from ammonia.