I have only had my Eco-Sphere for about a week. You will definitely be very pleased with any of these miracles. While I only have the little one, for myself, when the time comes to re-charge this sphere, I am most positively getting the largest one they have to offer. I love this Eco-Sphere so much that I just bought a medium sized sphere for my parents 65th Wedding Anniverary. The little shrimp are adorable. They require no special attention, no feeeding and are a joy to watch. Very peaceful. The packing is unbelievablely over-the-top. The Customer Service employees are very polite, exceptionally helpful, very knowledgeable and caring. Delivery is unbelievably super fast with an actual delivery date that is YOUR choice. Need I say more? No I am not being paid to write this review! Buy one for yourself, but if you can, buy as large of one that you can. You will not be disappointed.