Terraria Community Forums

Both. 200 tiles of grass for the biome to count as mushroom, and 200 (preferably 300) tiles of water to fish for it in said biome

So, how would you build something like this?

Hmm, I could make a screenshot example and send it here, but I need a bit of time to do that.

Thank you, though

This is a pretty simple design for an artificial biome with a fishing spot. Can also work for artificial jungles, crimson and corruption, though may need more blocks.
The reason why the mud is placed in a grid formation is so that you get more mushroom grass with less mud and less space used.

Thank you, honestly

Also, if you don’t mind, what are the dimensions?

Uh, I didn't really make any precise calculations. The mud grid is about 9x19 mud blocks, whilst the pool is 31 blocks high and 12 blocks wide (exactly big enough to fit 300 tiles of water). You can of course modify these dimensions to your liking, as long as the biome turns to mushroom you're all good