I have the 4 gallon baby biorb. I've never had at problems with it, its circular, and my fish always love to get the zoomies and swim in circles around it.
People on this site hate the tank, and I know that, but I enjoy it. They don't get sucked in the filter tube, because its not a filter tube, its an air pump. The filter is an undergravel air pump. The filter is a bit strong, but I've never had any problems with it. You can baffle it with a little piece of filter sponge.
I have river rocks on the bottom, which are smooth. I buy regular decor for it as well. Sorry I hadn't noticed this thread earlier!