Normally a 5-15 gallon brewer is enough for any gardener! The larger the container the stronger pump you need to really aerate the tea brew.
For a 5-10 gallon size brewer, many folks are using standard 30-60 gallon aquarium air pump bubblers, with multiple air tubes, for maximum aeration.
If you get the brewing container too big and the air pump too small, you will create a tea that is only partially aerobic with aerobic microbes in certain spots of the tea liquid, while other areas of the tea will remain anaerobic, with stinky potential pathogenic anaerobic microbes in it.
Also a good 5 gallon 100% aerobic tea brew can be diluted up to 1-5 times with non-chlorined water, and be used as a light foliar spray on an acre of crops, like tomatoes! A 15 gallon aerobic tea can be diluted 1-5 times, and used as a light soil drench for an acre of crops, like tomatoes!
You can create a 5-10 tea brew every 1-3 days if need be, and never turn your pump off. This is how I foliar and soil drench my entire farm of crops, ornamentals, and lawn.
There really is no need to create a super large tea brewing over 20 gallons for most farmers.
The entire Kingdom of God can be totally explained as an Organic Garden (Mark 4:26)