Hey folks, I have a 10 Gallon freshwater tank that has been stable for a month and a half with occupants (after being cycled for probably too long before that), which were a Dwarf Gourami and two Platies. However, about two weeks ago one of the two platies suddenly of toxic shock. Testing my water after that showed that for some reason my levels were very unstable. I've been doing water changes of about 35% every three days since then, and surface gravel vacuuming as well, but my levels have remained consistently bad. I've also been swapping my tank over in this period from fake plants to semi-planted, in hopes that I might be able to stabilize my nitrites, and in total I've added two Java Ferns and one Anubias. Despite this my levels have been continuing to hover in the dangerous zone. Specifically, in addition to the nitrite spike I've noticed my pH dropping and alkalinity hovering around zero. Last night I did a 50% water change in hopes of stabilizing them. With the water changes, I've been using Seachem Prime to dechlorinate, Nutrafin Cycle for bacteria, and Nutrafin Plant Gro sometimes for the ferns. When I tested my water today, the numbers were: Ammonia: 0.5 (this had been sitting at 0 prior to the water change) Nitrates: 20 Nitrites: 5.0 (which improved from the 10.0 it was sitting at before) Hardness: 75 Chlorine: 0 Alkalinity: 0 pH: 6.2 (which dropped into acidic from its previous 6.8 level) At this point nothing I've tried has stabilized the tank. While my remaining pair seem to be doing alright for now (regular appetite, not gasping at the surface, dg has even been trying to drag bits of plant to the surface to bubble) but obviously I want to get them back into safe waters ASAP. I've been considering trying to use a nitrite emergency dose of Prime to deal with that, but obviously that won't help with the pH, which I believe is a problem stemming from my tap water. I've also been looking at getting some crushed coral to raise my overall buffer, but again I'd rather get some good advice before trying anything else that'll mess it up further. Thanks for your time guys, and I hope I didn't forget anything important above.