Tote for sure.
I find that 5 gal buckets fillup with roots and displace too much volume in the bucket,
That makes it challenging to keep the solution stable because the plant is using such a large volume of nutes compared to the total in the bucket.
I use 17 gal HDX totes from HD, but they are too long to fit a pair in a 2x4.
The 12 gal HDX would fit nicely, I use 6" netlids on my system.
I'd also think about how you plan on doing dumps-need some type of pump/drain so now would be a good time to think about a solution.
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