Thanks for sharing what you are doing. ETA - That must be a HUGE bag of Multi-NPK; what a great price too.
I'm surprised it is so buggy where you are since it looks like you are growing on a deck.
Are you now growing in Tijuana or San Diego? Are the seasons the same?
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I don't notice any twigs in ProMix BX - I get it at the hydro store in the 3.8 Cu ft bag.
That said, on the last Vendor Day, I bought 3 bags of Happy Frog, 2 bags of Coco Loco, and got a 3 cubic bag of KO KO Bop for free.
Potting mix is really $$$$ where I live so I might as well go with the good stuff.
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Have you ever tried the coco peat slabs for tomatoes? something like this
https://www.amleo.com/Search.aspx?ss=fibredust