What is the condition of the new LR? Is it coming from someone tank, where they've had it for years and it completely cured, or are you getting it from a LFS, that may just have gotten it in? Also does the LR have have a lot of material that could die, like sponge or plant life? If it does than it's probably best to cured it in a pail or container before you place it in your tank.
If the LR is cured, with the possibility of very little die off or a spike, you could add it slow to your tank. The amount. of LR, is small and your tank should be able to handle the spike.