you should not be using a bucket for long term secondary aging of sours/lambics/brett beers. you will let in too much O2 leading to too much acetic acid production. if anything, start with a bucket and use the carboy, better bottle, corny or even better and oak barrel for long term aging. in wild brews there's a chart that shows how much O2 is let into each vessel. the bucket itself breathes, not the gasket or lid at the top, but the actual plastic itself. some have asked about submerging a bucket in water, but even that's prob not the best idea.
here's some talk on using an ale pail for secondary:
https://www.homebrewtalk.com/f127/age-sour-beers-sealed-plastic-buckets-181007/
and another thread with some good info:
https://www.homebrewtalk.com/f12/gueze-beer-recipe-byo-58780/index2.html#post600464
compliments of landhoney:
"Some oxygen can be good, too much is bad. From 'Wild Brews':
Type // Gallons(size) // ( O2 cc/L/year )
Rodenbach tun(small) // 3,168 // .53
Wine Barrel // 80 // 8.5
Homebrew Bucket // 5.3 // 220
Glass Carboy w/wood stopper // 5.3 // .10
Glass Carboy w/immersion tube // 5.3 // .31
The last number is how much O2 gets in contact with the beer per Liter per year. So the homebrew bucket is letting in waaayyyy more than any barrel commercial brewers are using. And I don't think the plastic 'flavor' ever comes out into a beer. People do leave beer in them for many months, and I've never heard of anyone complaining about this."