Status report
Hello all! I wanted to follow up on my current status and plans. I actually found out what the problem was--well, I narrowed it down to two things, both of which I have removed. The first was too stupid to mention, but here goes: I added styrofoam boards and poured the new substrate on top, which I thought would allow me to get away with using only one bag of the new substrate instead of the recommended amount and give height to plants and driftwood but that ended up allowing waste and dirt to accumulate on a large scale in a place that the siphon would never reach.
The second was that I discovered a bag of water softener and a bag of Diamond brand charcoal that I'd forgotten I'd put into the media slots of the power filter from I don't even remember when, maybe when I first got to the new place. Both things were stupid, not to mention costly.
But there is an upside: Having corrected the problems, I have had my interest in discus reinvigorated. Things are now going great in the tank. I bought a white-faced red melon from a breeder, which is doing great. All my tetra have survived more than a few days. I am no longer using any additional filter media, so I won't have to worry about forgetting and probably don't need anyway. My water is soft and good PH as is I found, so no need to reduce it. I've upped my water changes with a python to small (10-20%) every day or every other day. I got very discouraged after losing most of my discus, but now that I have learned some costly lessons, my fishkeeping skills have only benefitted. I will add two more discus to round it out. I found varieties that will go with the primary color scheme that my wife wants--the red mellon that I already have, a golden sunrise or some variety of solid yellow or gold (close to a saltwater yellow tang) and maybe either a solid white "snowflake" or one of those snakeskin types that are white with red net-like lines over it. My original from the first set who survived is brown on the body with an irridescent blue at the edges and on the fins and forehead. Unfortunately, he doesn't look great with rotted fins that were due not to poor fishkeeping, but because he was the runt that all the other fish beat up. Ironic that he was the sole survivor of my screw up. Once he had the entire tank to himself, he actually grew very big--about 6". I don't know if his fins will ever recover, but I'm hoping so. I will post pictures if I can, but I wanted to mention that so nobody wondered about the messed up fins.