i make both aerobic and anaerobic, there both good for diff things, aerobic you need a bubbler to air rate the water so that only aerobic bacteria stay alive, anaerobic is usually better done with plants, its the one i use most. i use comfree stinging nettle and alfalfa. you toss a lot of them into a bucked fill it with water and seal it (bBTW it stinks so be prepared ) the plant matter is broken down into nutrients and you can mix it with water about 1 ltr to every 20 and it makes for a good safe but smelly feed. i use it bout every month . i don't use anaerobic much but its really for building a good microbe culture and you only need to use it about once a grow, ive only done it once and i did it the way they do here. you take about 1/4 of steer manure and wrap it in cheese cloth or some thing similar , then you dip it in and drop the air stone in and let it sit for 12/24 hours . there is a thread in the Hydro forums al try and find it for ya