Hi Gail,
Thanks for your post. Sadly I don't think my tank is cycled

,
although I can see why it looks that way with NH3 at zero, NO2 at zero
and NO3 at 10ppm at the start. As NetMax said - it's the tap water. I
wasn't sure myself so I tested it and it's bang on 10ppm straight from
the tap - same as the tank.
I didn't realise, though, that I didn't have to do a cycle if I seed
the tank from an established one. As you can see I'm a bit new to
this. I shall probably continue now I've started but will bear your
advice in mind for next time.
Many thanks!