All seeds opened after 36 hours. I put them directly into cubes of rock wool, sunk about 5mm to 1cm, the next day the seeds came out, one of which was more than 1cm.
Day 3, I put them in 15x15cm pots, filled with "canna coco professional plus". I fed 4ml/l of rizotonic and 0.5ml/l of coco AB.