As discussed previously, there may be students in the class that are allergic to animal dander, urine and saliva. This generally limits the types of classroom pets supported by many schools. The best types of classroom pets are those that don't have hair or fur, shed dander, or produce excrement that creates allergic problems. Some non-biting or non-stinging insects are ideal to house in the classroom. Insects such as stick bugs, beetles, butterflies and meal worms offer fun interaction and observation opportunities, as they have quick metamorphosis stages and life cycles which can be easily incorporated into any curriculum. Worm bins are also a fun way to bring living organisms into the classroom safely while teaching about composting and the environment. An aquarium with fish and other underwater creatures such as sea stars, horses and urchins are ideal for a classroom. Although the budget must be available to maintain the aquarium students can enjoy watching and learning while having a continued sense of responsibility without the risk of allergies.