Nudibranchs?

Hey guys. Ive always been intrigued by nudibranchs and i would really love to keep one in my tank. People keep saying everywhere that they are "impossible to keep" but i beg to differ. I think keeping one in a aquarium is possible. I've been researching ones for sale and different species and im really liking the violet and orange nudi. http://ift.tt/1kWJU2u sells them. People say they only eat sponges and others say they eat algae. If anyone has any information on diet, care, etc. for this type of nudibranch (or any other ones) please let me know. I would really like to successfully keep one of these lil guys. An extraordinary specimen. Below i will post my tank specs if it would help any. Thanks so much.