[jmeeter]

Recently I pulled up a plant I no longer wanted in my aquarium and a huge cloud of yellowish "dust" came up with it. I'm pretty sure this was from a root tab I put in the substrate a while back. Is this harmful in any way or is it normal?

 

[Diana]

Test the water for all the usual suspects.
Often, if the fertilizer in the root tab is still there the ammonia level in the water will spike.

If the fertilizer is pretty much used up, then the remnant (highly likely a form of clay binder) should not affect the water quality. Might be unsightly, though.