Or sometimes they die from starvation because they are filter feeders. Some anemones require alot of light some don't. They need current to get there nutrients to them. But a wicked protein skimmer and an unexperienced hobbyist is usually the killer of an anemone. Keeping multiple anemones is more of a task since alot of corals are territorial and will kill each other and in turn poison the tank. Whatever happened to Nemo's anemone anyways he must be lonely.