Soiless can be many other things than coco fiber like expanded clay, rockwool, peat moss, the list goes on.........
Yes you do need to add nutrients to a soiless grow, if your lookinjg for a reccomendation I like to use the line on "Earth juice" brand ferts, it's pricey, but cheaper than so many other brands, and it's certified organic. One problem with it though it is low on calcium, which is easy to correct in a number of ways, I use powdered oyster shell it's cheap and available at any pet store/animal feed store.