I kept them with succes for 3 years. The dided all the rest of my fish when my grandmother overfed and when the powe died in the house while I was gone. Have you even tried keeping sturegons?I fine it funny to say "that worked good" when the fish are now dead...
I recommend separating them putting tropical species in one tank, and the sturgeon in another before problems start to occure. Considering it couldn't be more then a few months that you've had these fish together in your new setup it's not an example of success it's another example of someone in the process or failure.
Fish are tough it can take them time a long time to die from environmental factors but it will eventually kill them or weaken them to the point that some other issue finishes them off. Species that arn't tropical can often withstand the high temps for some amount of time just like they would survive hot summer months but it'll catch up with them eventually that's why they are not found in tropical waters in the first place!
the sturegons Ive had/have tolerate up to about 28C but I keep them in 23C