1. It is never a good idea to add shells from the beach into your aquarium. Introducing shells raw from the beach can add harmful bacteria and potentially new creatures to the aquarium.
2. You should take out any carbon filters in the aquarium when you are medicating your fish. The carbon in the filter will remove the medicine from the water, so it is best to remove it all together.
3. You should always take the time to acclimate your fish to the aquarium. Acclimating your fish will get them used to the environment of the aquarium. Adding fish directly can be too much a shock for your fish and can pose health hazards.