Lol fastback! "Make it feel like winter"
Plug the truck in, spray your Xmas tree and cactus in the front yard with tree flocking and don a scarf and touque. It all helps!
I can't stand being without winter time. Love it. 2 years in Phoenix were he!! For me.
I'd fire up the snowmachines in the garage! Cost less than therapy!
To the OP, if it's a plasti tank and out of the weather, I'd be fine with letting fresh diesel sit for a year, but my OCD would treat it with some Standyne and if humid (Missouri) I'd attempt to seal up the fuel tank vent. If it's in the fuel cap, a sheet of plastic or ziplock bag under the cap would seal it.
That said, in the better part of 30 years dealing with diesel trucks or equipment ive never seen diesel go bad. I've never experienced algae growth either though. My thoughts are that is rare and directly related to questionable fuel or storage practices in the first place.