400w of cobs for quality AND quantity dude!! In 1.2 x 1.2 space. In reality, 400w of cobs will do the same yield as 600w of HPS. And probably only use 200w during veg. Also I reckon 400w of proper cobs is worth around 500w of (315) CMH roughly.
BUT... 400 quid for 400w of cobs. But thats proper kit/components and a quality build. Honestly I was looking at 315 CMH lights but with my anxiety I just can't do flaming hot glass bulbs! Especially the one I'd want that hangs vertically! WTF?! Man I wouldn't be able to sleep.
Yes mate first try with autopots biotabs and coco. Did a Gorilla OG and a Jedi Kush. Both really awesome organic smoke, really happy with it for once. My Mrs loves it too. She says both are better than UK Cheese! You can get hung for saying that around here dude! Haha Jedi is surprisingly strong. Frostiest weed I've handled myself. Definitely strongest I've grown. Proper indica punch in the face and melting arms/legs/body feeling. Tastes and smells like bubble hash in a joint. Gorilla really good for daytime smoke. Lovely lemon, pine, sweet aromas and flavours.
I did what you're doing with dolomite lime and didn't get any calmag issues mate. I also added some PK booster compost tee as I saw Sir Tabs does that.
Will be following this journal for inspiration and guidance dude.
Right, decisions to make about strains!