Walikumasalam Warehmatullahi Wabarakatuhu,
Umm I'm pretty sure that I'm not aware of any 'fish thing popular' over there, if at all it would be normal fish in aquariums that's all...
Can't help you much there...
For chocolates, every brand and such are available here in Pakistan in big stores, but still you can ask him to bring you: Ferraro Rochers, Tobelrone, Galaxy Jewels/Galaxy Flutes, Maltesers etc
There's a mid-quality brand that I'm not sure is available here that is products of Ghandour, chocolates named SAFARI, TOFILUCK, PIKONE, HAWAII, SAHARA etc
All others like M&Ms, Mars, Twix etc all are available here...