I'd say driftwood leaching. Lost several Discus because of nsame. New 44 gallon tank set-up, that I used all accessories from a cycled 29 gallon. I had to tear it down completely and use a razor blade to remove driftwood and set back up. No deaths after that. Good luck.

Thanks. After several large water changes, carbon and Purigen in the filter...and time, I now have three shrimp that have settled in. Nerites still looking good.

I really like the scape that I have and so am still dragging my feet on pulling the one driftwood "suspect" that is the center piece of the tank and holds back a lot of aqua soil from the sandy front "beach".

Really good news.

Looks like the water changes, Purigen, and carbon have paid off. I pulled the prefilter on my Oase pump and actually found a baby shrimp. That was a surprise. The adult shrimp are showing more normal behavior, as in grazing and not running laps around the tank. I now have several nerites and also two Ottos who gratefully seem unfazed in that low key Otto sort of way.

A good day.

Based upon moving a few shrimp, and fish slowly over a week with success I did my migration today.

25 gallon rimless Landen tank to 75g Waterbox. 3 hours of moving the rest of the fish and shrimp along with selected plants.

Everyone looks healthy although a bit beat from being chased by the Net Monster!

Thanks to those who offered suggestions. Still not sure what the issue was.