Canna D Block All Canna products have gone through years of testing and tweaking to get them just right, the Dutch Giant is synonymous with high quality, great taste and heavy harvests. Canna D-Block will prevent blockages by inorganic salts in automatic feeding systems and feed lines. Canna D-Block will not harm plants and can be added to every feed. When preparing your nutrient solution be careful not mix them together in their concentrated form. Add each part of your nutrient schedule to your tank separately, mixing thoroughly before adding the next component to the mix. Canna D Block feed rate – 1ml /10 Litre in Growth and Bloom.