There is only 1 female pearl gourami, which I doubt could decimate a
snail population of a 72 gallon. Either way, the group seems undecided
on the cause of death of the snails.

I will take everyone's advice and try to solve this problem. Firstly,
I will locate some Profile and add another inch or so to the substrate
so the snails can burrow more successfully and hide from the kuhli
loaches hopefully. In the 55g I will raise the kH to a level
considered more normal instead of .5 or 1 degree, I will keep it at a
level of 3 or so and as a result the pH will likely rise from 6.6 to
around 6.8, more habitable for snails.

Either way it has been puzzling, without any real answers (I feel). I
appreciate all the conjecture on the subject, however. It has led to
new ideas that I had not thought of.

Ive heard that a lot of Anabantids (guoramis in this case) will destroy snail
populations