Would It Be Silly To Use 'spots' Of Plant Substrate?

[Rynofasho]

Getting ready to plant the 75 and I'm getting a few swords and other heavy root feeders. My substrate is going to be about 3" of play sand, so nothing all that great in terms of nutrition. That said, would it be a bad idea to throw some ecocomplete under the areas where I know I'll have the heavy root feeders, or just stick with root tabs?

 

[KkAaNnEe]

I have a 75ish tank with just sand, the swords aint doing great so i have opted for root tabs. Thing is with spotting thw plant sub is that you may move stuff around in future etc