They are awesome to look at, but are very demanding as far as care(heavy flow area on the reef and ... I strongly suggest a very established aquarium. Butterflies will tend to nip at their feeding appendages while they're(the apples)are feeding from the water column. When stressed, they can exude holothurin(their toxin). Even if kept without duress, their eggs are extremely toxic to fish and will cause death. FWIW, I've had mine for about 3 years and it's ok for now, but there's always that chance.