Update. OH MY GOD. Started water change at 5:30, finished at 8:00. I completely removed all fish all water and all plants, rinsed the gravel and took out all crap, washed filter (not media), and redid whole aquascape. Tank looks great now, fish look even better. Damn that little clown loach was tough to catch. First of all he refused to come out of his log. I had to take out the log and physically pull him out of one of the holes by his tail. and then catch him with a net, because I dropped him, and for those of you who have loaches you know what a pain in the a** that can be, even in 4 inches of water. They shoot around so fast it's like lightning. Anyway, then came the water change. All I can say is:
46 gallon tank + flight of stairs - python = the hardest, most tedious, tiring and boring thing you have ever done.
I'm bushed, but overall it's rewarding because the fish are looking very happy and invigorated by the fresh water, especially the discus. I'm finding it harder and harder to get used to the idea of getting rid of them, I may just keep them and go with option 2

. Anyway phase 1 of my plan is complete. Wish me luck in the future. This weekend I will probably return the clown loach and discus if possible and buy the danios. (And the 2 gallon for Charlie). I am wondering though. If, since tiger barbs are definitely a must for this new setup, would they get along ok with Charlie if they are in a large group (10-12)? If so I don't really need to get a new tank for him and I'm sure he'd be happier in the big one anyway.