Dempseys are damn near bullet proof mine survived all of my newbie mistakes and a bout of depression where I did not take care of the tank right for a couple months. Mine lived 9+ years. Hopefully this one will do the same. They are awesome fish.
Good thought, when I kept them in the storage tub for 10 hrs while tank setup was going on I added their "poop" water to it (about 30% poop water). I completely replaced the substrate but kept some old substrate and re-used most of of the rocks/deco and bio media etc. even on day two I had a nitrate reading of 10-20 ppm, and it slowly rose to 50ppm until I I increased water changes from 20 to about 35 or 40%. The nitrites started about the fourth day and have been way to high (2-5ppm) for the last few days even with daily water changes. I think tonight I may do a 50% water change with some PRime treatment and wait 24 hrs to test again. What do you guys think?Congrats on a job well done.
Just a thought; I was thinking the following while I was reading your post.
If I was in your situation I would watch for Nitrate poisoning (damage already done). If he didn't do a water change for that long you can be sure that the Nitrates were sky high. While high Nitrates might not kill a Jack or convict out right it weakens the immune system leaving the fish susceptible to disease. The move obviously causing some stress, and the quick change from high Nitrate in your buddies poor care to low Nitrates in your good care might further weaken the immune system. Only thing you can do is keep the water supper clean and be handy with meds if it happens.
Good luck and great Job!