I am feeling like a fish executioner at this point. I have had two tiny tanks for 6 months and a year respectively and have had great luck. Didn't know about cycling, but my son gave me lots of material from his established tanks, filter material, plants, etc. and the only things that have ever died in those little tanks are a few shrimp. I've only ever used dipstick tests for these little tanks and everything has been fine. So, I wanted to try a 20, and bought a kit on deal from the lfs. Advice from lfs and my son was that cycling with fish would be possible if I imported a lot of material from my other tanks, put in lots of plants, same as with the tiny tanks. I also bought a special wet bacteria-infused substrate that I was told would help with fish-cycling as well as plants. My readings were ammonia .25, nitrite 0, nitrate 5.0 consistently from set-up until now, 7 weeks later. (One odd thing was right after set up, a weird material appeared in the tank at the base of the newly planted plants, kind of like little plastic chips, which I vacuumed up, but the lfs guy said there couldn't be anything toxic in the plant packing materials. However, there was also a weird smell, which is now gone, that I found chemical-ish.) Nevertheless, things have been consistently dying, slowly but surely. I lost 4 of 5 S&P corys, 3 of 6 danios, 2 shrimp, a gourami, and a guppy. Two mystery snails are fine. One of my sword plants is not doing well and I clipped off the sick leaves. My son put a bunch of baby guppies in to see if that would help, but I feel like I'm just leading them to slaughter. I tried some ammo lock, thinking even the .25 reading was causing fish death, and in the last couple days the ammonia reading spiked to 4.0. I have found contradictory info online about ammo-lock causing false readings. I just don't know what to do at this point. I have done 25% water changes in the past 4 days, but the ammonia readings are the same. At some point do I just break the whole thing down and start over? Sorry for the long saga, but I just feel awful about this.