Sorry guys, but I respectfully don't agree. Ottos do not get very large at all - probably no more than two inches. The first ones I got were in a 2 1/2 g tank with my betta and it is now 3 years later and I still have them although they have moved up to the 10g but they are no longer, just a little fatter. The big thing is they need to have a source of algae so you don't want to put them in a new tank and even after - depending - you may have to feed them some algae wafers or as OC, does, grow some algae logs.