Although I do not live in the U.S., but in Germany, post here yet.
this is my PRIVATE own opinion, but did with Gerd Kohl and Erich Mayer talked about it in detail. I had the plants at least 5 years with no problems.
I have unfortunately lost the plants at mienem move about 7 years ago. It was in the middle of a severe winter. The plants were for a short time in a warmer room. Had begun to end their hibernation and again get light frost.
My experiences are that arietinum is very susceptible to infections.
I had, in principle, I acaule suitable substrate, but not so sour.
But pure mineral, absoltut scale-free, with layer of moss. (sphagnum)
Pour from the bottom. In the winter, "iron dry in summer wet but no water.
The lime-free humus-poor slightly acidic substrate is probably also low-germ.
The living Sphagnum cover to do his.
Cultured in dishes. To keep flat roots on the surface, helping the sphagnum moisture uniformly.
Arietinum seems to have the tendency to drive out quite early and is then extremely sensitive to late frost.
The plants themselves need definitely no fungus. I've tried to bottle product.
But there is no available free of fungi in nature, it may perhaps be useful if acaule grows in a location that is already occupied by a relatively harmless fungus. Whether this is a "guard mushroom" I doubt it.
Stop behaving like apifera, mascula and co ... or just acaule!
PS: I cultivate recently for 3 years a acaule uerfolgreich under the same conditions. But seems to be a clone that is not too acidic.
The main thing Keinarm .... I guess ....
regards
Bernd