The ‘tub’ people are speaking of is called a swamp cooler. Do a google search (add beer or homebrewing in the search so you dont get the swampcooler AC type things) and you will see tons of hits and some pics to help you better visualize it. They do work well once you figure out your system. But if you can save up, search craigslist and find a fridge and then buy a temp controller and you’ll be able to have so much more control over everything. I know it was your first batch, but you will see, you always need more toys. Good luck