At one point I owned 8 Worthington HP100s ... 3 sets of doubles and 2 singles. They are the perfect tank for me! I broke down one set of doubles and sold two sets leaving me with the 4 singles I still own. I sure wish I'd not sold one of the set of doubles. I would love to have 6 singles instead of just 4. Oh well, hindsight is always 20/20.