Not surprisingly I'm going to suggest something native. Perhaps take them on a collecting field trip? Get them involved and establishing a relationship and appreciation for not only what lives in their backyard but the outdoors itself. My kindergarten teacher was always taking us out to small ponds and such, collecting tadpoles and small fish. I think it stuck with me.
A pictus catfish and Africans? I realize they're first graders but I think you should at least do a bio-tope (a true window into another world) with fish that occupy different levels of the tank. You can get them started on learning about the interactions between different species and the niches they occupy. If you go with relatively peaceful fish you won't have to worry about any of them dieing or in the case of easy breeders trying to explain the facts of life.
A pictus catfish and Africans? I realize they're first graders but I think you should at least do a bio-tope (a true window into another world) with fish that occupy different levels of the tank. You can get them started on learning about the interactions between different species and the niches they occupy. If you go with relatively peaceful fish you won't have to worry about any of them dieing or in the case of easy breeders trying to explain the facts of life.

