Planted Tank Guru
Join Date: Jun 2004
Location: Baton Rouge, LA
Nothing terribly new. There's already commercial plastic pellets for this, like NP-Active Pearls. And long before that, folks were using cheap vodka as the carbon source.
But if you use nitrates to grow lots of bacteria, then you have to remove them with a protein skimmer or frequent filter cleaning.
If allowed to remain in the tank until they die, they release ammonia. Which will be converted back to nitrate by other bacteria. And nothing will be gained.
Plus remember water changes remove all buildups, not just nitrate.