I have repeatedly gotten mine to a good 2.5-3" and as thick as my thumb when kept in room temp. The ones in with my fancy goldfish right now are that size. They also hit that size in one summer in a pond.
Exactly. Maybe it's the case though as i don't seem to be able to find any info on the net regarding them. They just seemed huge, like 4" big! Mine have never reached this size even in a decent sized aquarium. They reach about 2" and thats your lot.
Strange. But not worth a fiver each if they're about done for!