I built Hellivators to separate my biomes AND a subway system to create even more gaps to prevent biome spread. I mentioned it in a previous post:then you guys probably didnt builded walls with empty pockets around it, so ofc nothing stoped it to keep spreading, I did that on all my biomes, ocean, snow, desert, my crimson is contained. Also I spreaded hallow around the jungle so it actcs as a natural barrier as well.
As an Autistic with a side case of OCD, (which isn`t uncommon, look it up), I can agree with this. When I dug my Hellivators to protect against biome spread for when I finally throw my world into Hardmode I took extra time to dig down the edges of my Ocean biomes, replacing the sand with Obsidian brick until I dug past the Ocean. The rest of my digging basically resulted in a Hellivator with the top capped off with Obsidian brick. No ing way i`m letting Corruption get where I can`t reach!
5 or 6 blocks wide and I didn`t lose my Oceans because I took Gills potions with me and dug down, filling the openings above me where the sand used to be so the Ocean wouldn`t drain out through the hole I was digging. Only a small amount of Water was lost by doing this.