Compare prices with Bells (and shipping)https://bellsbeer.com/store/search.php?search_query=carboy&x=0&y=0
Why? Just use 6 gallon. I brew 5 gallon batches in my 30 gallon primary if my others are busy. Well not anymore I have a ton of fermenters now but I used too.
My Recipes: Drunken Emu Hard Cider, Drunken Emu Mississippi River WaterThe Jack Keller Collection
Good to know. Go big or go home then!