After 4 leaves established i repotted the plant into its final pot, a 15l felt pot. The plant is developing okayish, neither super great, nor bad. It's probably a bit stunted by the low temperatures but i think it should be fine in the 20°C range. When the plant grows a bit more, I can increase the light and therefore the temperature.
This week I'm also starting to add Bio-Grow to the mix.