Well this experiment has taught me a lot. I now know there are 3 places your nutrients can go. The water, your rocks, and your small scavenger creatures, especially things like bristle worms. I think part of what happened to me is that all the over-feeding built up and caused an enormous algae issue. I really didn't think that feeding once every other day was too much but apparently it was. Also in the beginning I was feeding pellets which probably didn't help.
Thankfully I was able to observe all the creepy-crawlies that would come to life after the lights went out. There were definitely too many of them. I might go so far as to say that if you see bristle worms in your tank you're feeding too much. Right now I feed once every 3 days and the fish are alive and well but there are no longer such things as bristle worms. So there is a margin between feeding your fish and feeding the fish AND the worms! For me the 1 block of brine shrimp with selcon once every 3 days is enough. The current fish being 1 tang (and yes he eats the shrimp), 1 clownfish of medium size, 1 small clownfish, and 1 cardinalfish.
So yeah, right now there is algae growing in that scrubber! Still a bit of film algae on the glass but no hair algae in the display. I think the obsidian is working as intended. Now the nutrients have nowhere to go so they just stay in the water until they run into the scrubber.
If I see some level of success with this, I can start trying to make the tank more interesting again. I made the mistake of buying coral when I had not yet dealt with my nutrient issues. Also I bought too many. Buying a million zoas at once seems to be a bad idea. Maybe they are just too aggressive with one another to exist in a system as small and closed as mine. So yeah it's like a big 200 (or was it 400?) dollar zoa massacre that I totally regret.
At least this entire time I kind of had the right idea to run this as an experimental tank to learn on.
The next step is to amp up into putting normal reef rocks back into the tank. Then if I somehow pull that off, the step after that is to actually start a tank and have it succeed with normal reef rocks with no water changes. By then I will have finally defeated water changes completely and utterly! For both freshwater and saltwater.