Masdevallia Aquarius is a hybrid that was bred to be the first step in creating temperature tolerant Masdevallias. Nights at 65 F are probably ok, just a few degrees cooler would be perfect, say 60 to 62 at night. No need to drop temps below 58 F. I often grow my Masdevallia in sphagnum, the 2 parts sphagnum, one part perlite is a mix I often use too. And because I get them in a bark mix, I have grown them in bark mixes. I like the growth in sphagnum. Masdevallia do not like to dry out completely between watering. Keep at least a little damp. They are a pain to get roots on once the roots have been lost. Don't give up yet. Most of the Masdevallia hybrids are sun lovers, they want more light than a Phalaenopsis, up to about the low end of the amount of light as a Cattleya. Failure to thrive is often related to not enough light.
Second cause of loosing roots and not thriving. Sunlight hitting a plastic pot and heating the plastic up, cooking the roots. I routinely set Masd. and Miltoniopsis that are growing in plastic pots into taller, larger terra cotta pots. I leave the space between the inner and outer pots empty, for cooling. The outer pot keeps the sun off the plastic, allowing you to get direct sun on the leaves and yet keep the roots at ambient temperature. Masdevallia roots are sensitive to high temperatures. This really helps. It is essentially a simplified version of a Zeer pot, it does not require the evaporative cooling you would get with a Zeer pot. By the way, a Zeer pot would work also.
I summer most of my Masdevallia outdoors, but I am near a Great Lake, and most summers I have fewer than 14 days above 90 F. In your area this might not be a good idea. Masdevallia like 'eternal spring' climate, not too hot, not too cold. When outdoors the wide day night temperature drop is helpful.
Hope this helps.
