"No, I do not see anything."
Translation:Nee, ik zie niets.
If you're using 'iets' rather than 'niets', the negation is not in the sentence anymore. It would be 'ik zie iets'. You can't use 'iets' in this sentence with a negation ('Nee, ik zie niet iets' is not correct Dutch). EDIT: see my post below for different ways to negate sentences with 'iets'.
No. I have to rephrase. I've made a small correction to the previous post, i.e. that you can't use 'iets' in this sentence with a negation.
The non-specific 'iets' is negated to 'niets', the specific 'iets' is never changed to 'niets':
- Je hebt me iets niet verteld (There's something you haven't told me)
Je hebt me niets verteld (You have told me nothing)
Ik doe iets niet (There something I don't do/will not do)
- Ik doe niets (I do nothing)
Hope this will help!