hi GiGa, you see you dwc well you need some growing medium in the top part, and where you see the pic where you have got the stem coming through the lid of the bottle, well you dont want any stem that at all, you need to grow the plant in the top part and allow just the roots to grow down into the res, i use compost in the top about 3 inches and then plant the clone or seedling into this, then over a few days the roots will grow down and come out the lid of the bottle and this is when i fill the res up, then the top part supports the weight of the plant, if you have nothing their then the weight of the plant will just push it into the res and it wont be able to support itself,
so i start mine in compost then fill the top part with few inches of compost and plant the plant in that, then wait for the roots to grow down into the res then fill the res with nute mix, remember to use the stated dose for the age and size of the plant, now im not sure what you want to use in the top part, but you do need to use something, you dont want the stem that low down, all you want is the roots growing down into the res, the stem of my plant sits in the compost in the top part and then the roots go in the res and grow like crazy, ill try and find you some pics and post what im saying
so i start mine in compost then fill the top part with few inches of compost and plant the plant in that, then wait for the roots to grow down into the res then fill the res with nute mix, remember to use the stated dose for the age and size of the plant, now im not sure what you want to use in the top part, but you do need to use something, you dont want the stem that low down, all you want is the roots growing down into the res, the stem of my plant sits in the compost in the top part and then the roots go in the res and grow like crazy, ill try and find you some pics and post what im saying