I agree with Snowdrop. I've used a compost last year that seemed to have loads of stones and bits of stick in it, so when I sowed this years tomato, chilli and aubergines on the windowsill (ever the optimist) I sieved the compost. It was much easier to use with small seeds, although I think I would add a bit of vermiculite next time. I don't intend to do that for courgettes, squash, beans peas etc. At the end of the day it gets dark - sorry - I mean it all depends on what works best for you.