I have a pea puffer, guppies (male/female) and cherry/amano shrimp in a 10 gallon heavily planted tank. the puffer/guppies don't bother the adult shrimp but will nip at the smaller ones. of course, the shrimp have LOTS of hiding spots within all the plants. large snails will be ignored by the puffer most likely, but this greatly depends on the puffer's individual personality and how confident it is. it might nip at the snail, which will eventually kill it.. that being said, 2.6g isn't really big enough for anything other than the shrimp and snail.