1. Purchasing fish that feed off of algae is a good plan to take care of an algae problem in your aquarium. You could also try cutting back the amount of lighting in the aquarium or get an algae treatment chemical to take care of any algae problems.
2. When adding new species to your aquarium, you have to ease them in. Adding too many fish too quickly can cause the ammonia and chemical levels to raise quickly. Adding fish slowly gives your filter time to catch up.
3. 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.