About 5 years ago I made a couple of 5 gal SWCs like these Global Buckets.
https://video.search.yahoo.com/yhs/s...838b6ef69f762d
I put a lot of fertilizer in the top like they did, and I used white plastic to keep the heat down. I probably used a little water soluble fert in the feeding water too. They worked ok, but I had a pretty severe BER problem.