The tank is 20 gallons, storage bin is probably double, but only filled 1/2-way because I didn't trust the thin plastic to not break. I didn't add new substrate to the tank, but I did mix everything up when I built the hill back up and I took out some rocks, wood. The substrate is around 4-year-old eco-complete. I ended up not putting my fish in the tank out of laziness the other day and I'm glad I didn't because it suddenly spiked to 8.0+ ppm ammonia the next day. I assume it's from dying roots and all the stuff that was hidden in the dense plants that I couldn't vacuum up. I have done 80% water changes daily since, but since my water source has 1.5ppm ammonia, it's not a perfect solution.
Later I will buy water for the storage bin since there's no filter on it and it hasn't been cleaned yet...oops. I don't have a spare filter, but the bin has a heater, air pump, and the old hardscape(minus substrate). I will also check my LFS for the bottled bacteria that you guys are talking about. And I was thinking to get some floating plants like duckweed temporarily to help clean the water, just so my fish don't stay in the bin for so long.
Thanks for the help, guys!