De or het grondeling?

The correct Dutch article is:

de grondeling

Rule Words ending in -ing: almost always de. See the rule

How to use grondeling

the grondelingde grondeling
this grondelingdeze grondeling
that grondelingdie grondeling
our grondelingonze grondeling
your grondelingjouw grondeling
every grondelingelke grondeling
which grondeling?welke grondeling?
a big grondeling / the big grondelingeen grote grondeling, de grote grondeling