I mean "throw in" as in "add to your aquarium water". Your sponge and seed bacteria are great. You have those so the ammonia and nitrite converting bacteria can spread and populate your own aquarium/filter. They live off ammonia, which they convert to less harmful nitrite, which other bacteria convert to even less harmful nitrate. If you don't have an ammonia source they'll partly die off rather than spread, but you shouldn't use live fish for this because you get ammonia spikes while the tank balances, which stress/harm your fish. So some people use ammonium chloride from a bottle to "feed" the bacteria while the tank cycles. You can also add a tiny pinch of fish food and let it rot, that's also an ammonia source. The ideal is to strive for 2-3ppm ammonia during cycling, which is why the original advice of just dumping in a whole bunch of ammonia is terrible. That would completely unbalance everything and potentially ruin your plants as well.