What constant temperature changes? The outside will always be colder, but the water should maintain a steady temp if enough wattage is on his heater. Barring him piling snow against the tank suddenly, there should not be a temperature change drastic enough to crack the glass.
There will definitely be constant temp. changes. Depending where in NY, could be anywhere from 10 to 30 degree swings simply between day & nite. (Not to mention ice/snow storms of varying intensity & duration from early, mid & late winter.) I doubt seriously if the avg. 30g glass tank is constructed to endure these types of constant temp. changes for 3 to 5 months but I'm no expert so I guess you could try. (I wouldn't!!!) As stated, Con Edison is gonna luv ya trying to maintain that 80 degree water temp. thru the entire winter. I suggest a plan 'B' !! "T"
you would need like 3 300W heaters and that MIGHT keep it at 80 if you have the bottom, top and 3 sides insulated... the bigger the tank the easyer it would be to keep heated but even then you need some serious heat..
i kept my arowana tank 100 gallon glass outside during the winter with 2-250 watt heater, but it was in southern california , coldest is probably in the 40s, at night
There will definitely be constant temp. changes. Depending where in NY, could be anywhere from 10 to 30 degree swings simply between day & nite. (Not to mention ice/snow storms of varying intensity & duration from early, mid & late winter.) I doubt seriously if the avg. 30g glass tank is constructed to endure these types of constant temp. changes for 3 to 5 months but I'm no expert so I guess you could try. (I wouldn't!!!) As stated, Con Edison is gonna luv ya trying to maintain that 80 degree water temp. thru the entire winter. I suggest a plan 'B' !! "T"
I hear ya neighbor. "NYC" would be on the low side of the temp. swings. I was thinking a bit more drastic & brutal winter changes like Clinton Cty. , Chautaugua Cty. , Orleans Cty. , heck even the eastern tip of Suffolk Cty. All of these experience temp. changes far in excess of what an avg. 30g glass tank under pressure was designed to withstand. Gradual changes just means it won't fail instantly but the constant 'tug o war' between minor temp. shifts inside vs major temp. shifts outside will stress this tank to fail. The risk far outweighs the benifits (whatever they may be). Not to mention the cost of trying to maintain the 80 degree temp. !! Like I said before, I'm no expert but then again you don't have to be a doctor to know insanity when you see it. (not saying you or anyone else is, just the plan ) A plan 'B' is definitely needed JMPO "T"
There will definitely be constant temp. changes. Depending where in NY, could be anywhere from 10 to 30 degree swings simply between day & nite. (Not to mention ice/snow storms of varying intensity & duration from early, mid & late winter.) I doubt seriously if the avg. 30g glass tank is constructed to endure these types of constant temp. changes for 3 to 5 months but I'm no expert so I guess you could try. (I wouldn't!!!) As stated, Con Edison is gonna luv ya trying to maintain that 80 degree water temp. thru the entire winter. I suggest a plan 'B' !! "T"
!! Like I said before, I'm no expert but then again you don't have to be a doctor to know insanity when you see it. (not saying you or anyone else is, just the plan 
) A plan 'B' is definitely needed 
JMPO "T"
