Lets see pre-made carbon scrubbers are matched to fans for air flow. So have to look up CFM and figure out what works right for you situation.
On DIY Well just google Carbon Scrubber there are DIY and Videos ... LOL Videos can you dig it?
Times are changing.
Soil.. My point of view is that most good soil mixes are just a start and that feeding the soil by top dressing is what really makes plants grow buff.
Wikipedia.org is a wonderful place to explore the concepts of soi like the Soil food web. Trust me bacteria eat materials and even in pots the soil food web works.
But for a first time grower you can mix compost, peat + coconut coir + perlite to get a base soil.
Minerals are important as well as the other nutrients.
http://en.wikipedia.org/wiki/Plant_nutrition
http://en.wikipedia.org/wiki/Soil_food_web
http://en.wikipedia.org/wiki/Rhizosphere
i use rice flour , fresh ground coffee, azomite, Epsom salts, bone meal, green sand, compost, and crushed oyster shell plus more and grind up in a coffee bean grinder then sprinkle.
Oh I an trying to get away from sea bird guanos but the come in all strengths.
feel free to ask me more.. what you decide is on you but I do thing this way.