You can plant in clumps but it will take longer to fill in. I planted mine about 8 weeks ago and I started out planting it one by one. But when I got to the back of the tank, I got "irratated" with my back hurting from the hours spent bending over the tank, that I started to plant in clumps just to get the job done faster. 8 weeks later, the front of the tank looks great - nicely filled in, but the back of the tank still has a lot of empty spaces. The choice is yours....me, I'm going to undo the clumps in the back and re-plant them one by one this weekend.
Eheim Pimp #304
Victor Pimp #21
55gal planted, Eheim 2215,2-65w coralife 6700k cf,flourite w/super naturals tahitian moon sand, EI dosing, Angles, Ottos, Neon Tetras, SAE, Yoyo Loach
35gal high planted, Eheim 2215, 1-96w coralife6700k cf, flourite sand, RCS
2 - 10gal planted shrimp tanks