Don't those things get huge? I've seen them at like 12-14" across before, I think one of those would eat my tank
Yes, they get huge. My original Giant Cup reached 16inches before I moved it. The babys in the other picture were from pedal laceration when it was moved. In October '08 those two were about 1 cm across, now they are both close to four inches.
16 inch Amplexidiscus fenestrafer.