I like to have Apistos in my tank, but they don't survive for a long time. They seem to be ok for around two months, then they stop eating and die.
Other fish are ok, I even have some wild caught fish from Peru that have no problems. Also my Amano shrimp are doing just fine.
I also have a non CO2 tank with Apistos, no problems here. This tank runs on the same tap water, so GH and KH are the same. Soil and temperature are identical.
The only difference is CO2.