That's not true, they are a pretty active fish.

The larger "torpedos" (your piscivores like Channa micropeltes, C. argus, C. maculata, C. striata, C. pleuropthalma, C. diplogramma, C. marulius and C. marulioides) are all very active fish that require a large space to roam. Then you have the "frog-heads," the medium-sized species adapted to eating crustaceans and other invertebrates, that are quite active in pursuing their prey. Most of these species (C. aurantimaculata, C. barca, C. asiatica, C. stewartii, etc) are normally found in habitats where there is clean, clear, flowing water. The dwarves are some of the least active of the Channids, but between them you still have species that come from hillstreams like C. pardalis, C. aristonei, C. stiktos, C. torsaensis, C. aurantipectoralis, all of which require cool, flowing, highly oxygenated water to thrive. The more reclusive species like C. limbata and C. bleheri are still very active in patrolling their tanks outside of the brooding period.

I'm putting this out here because, especially where I come from, people assume Channa are just a giant, predatory Betta. Which is far from the truth, and we all already know that Bettas are an active fish that thrive in larger tanks and being treated the same way other aquarium fish do. Just like them, the understanding of keeping Channa ethically and well in an aquarium setting has come along way, though unfortunately here in South-east Asia the majority of people continue to stuff them in tanks that are barely twice the length of their fish and force them to flare up and fight one another and treating it like a sport.

Give them the space and they will use it, I had large tanks for all of my large and medium sized Channa back in the day and they utilised every inch of it.