There are many starfish which are not reef safe like crown-of-thorns starfish and chocolate chip sea star. Shrimps Peppermint shrimps, cleaner shrimps, pistol shrimps, anemone shrimps and blood red fire shrimps are better choices since the commonly available banded coral shrimp can kill fish, and the mantis shrimp will kill and eat most animals in a tank. Snails Some snails are parasitic but are rarely, if ever, offered in the saltwater aquaria trade. Sponges Tunicates (sea squirts) Reef unsafe Fish Non-dwarf Angelfish This includes any of the larger angelfish. Non-planktivorous Butterflyfish Eat mainly or exclusively coral polyps Non-planktivorous Triggerfish This includes most triggerfish. Most triggerfish are highly aggressive carnivores that will eat many smaller fish and invertebrates in an aquarium. They also grow to be quite large. Invertebrates Sea apples Currently short-lived in aquaria. They release a highly-toxic substance at death, decimating the aquarium. References Fishkeeping