When I lived in Wisconsin, I also kept a patio tank here and there.
But temp swings were my ultimate concern, so to maintain even semi-stable temps, I used my in ground ponds as sumps.
Without the pond for stability, swing from 80'F during the day down to 50'F at night was not uncommon, even with the pond as a sump night temps in the 60sF to mid 70sF during the day were normal, in up to 300 gallon tanks.
Fish had to be chosen carefully to handle the night cool downs.
Being into cichlids, I found many could not handle those swings, and many failed during cold spells.
I found Uruguayan and "northern" Mexican species worked best.
Below a pair of Australoheros sp Red Ceibal, in the outdoor tank pictured above.
Gymnogeophagus also worked well.
Herichthys carpintus, Geophagus brasiliensus, and some Tilapia could also handle the swings, but my outdoor window in Wisconsin only lasted the few months between May and late Sept so not the most relaxing of pursuits.
But temp swings were my ultimate concern, so to maintain even semi-stable temps, I used my in ground ponds as sumps.
Without the pond for stability, swing from 80'F during the day down to 50'F at night was not uncommon, even with the pond as a sump night temps in the 60sF to mid 70sF during the day were normal, in up to 300 gallon tanks.
Fish had to be chosen carefully to handle the night cool downs.
Being into cichlids, I found many could not handle those swings, and many failed during cold spells.
I found Uruguayan and "northern" Mexican species worked best.
Below a pair of Australoheros sp Red Ceibal, in the outdoor tank pictured above.
Gymnogeophagus also worked well.
Herichthys carpintus, Geophagus brasiliensus, and some Tilapia could also handle the swings, but my outdoor window in Wisconsin only lasted the few months between May and late Sept so not the most relaxing of pursuits.