I just returned a MaxiStack because 90% of my cartos didn't seem to work. Now I have a replacement and its so weird, I have a cargo w/ a 3.5 tank that works but I have several others that do nothing. I think they're the same cartos and I have no idea! They all work on my Bolt but not on the maxi. I thought originally it was defective but I got a replacement Maxi and have the same problems.