Amazon swords are tough as nails. Mid-high 80s wouldn't negatively effect them. Problem with Amazon Swords is, one they take-off, they get huge. I mistakenly started one in a 10g. Moved it to one of my 55s and I have to cut it back or it would outgrow a 55g. I wish you luck and lots of patience with the fishless cycle by adding ammonia. This is how I started back in the hobby in ~2012. It was a long process for me. I would search high/low for good used filtration media to start a new tank up now (if I didn't already have tanks to swap filters around in). If you're in the Buffalo NY area, I'd give you a sponge bubbler filter and you'd be off and running, ready to stock.