Typo in my post above - 2 gallon of soil is equal to about 8 liters.
Interesting that weeze likes the powder fert use as he's the first to say so. I've been talking about that here in plant problems for years. People used to think I was full of it but that was the group of years ago that insisted root rot was the source of all problems.
weeze, you meant "dry out" right? not "never dry out." you want the soil to dry because that's the only way that oxygen gets to the root zone. this needs to happen. It's why you put air pumps in a dwc grow or use sprayers in an aeroponic grow. Need that oxygen to the root zone.
The powder ferts are great for growers that don't know how to hydro too well or just want a "water and forget it" approach. There are other brands for this like dr. earth and whitney farms.
Here's a site that has a lot of great info. Marijuana Nutrient Problems