(not from the net!)
The above fish is Channa argus, the northern snakehead. In Korea, where I grew up, the species is fairly common. Channa argus prefers shallow weedy ponds and lakes with lots of vegetation. Northern Snakeheads are caught with live bait (often weather loaches). They guard the nest during summer and they can be easily caught with artificial lure during spawning. In the same pond where channa argus are caught, there are usually a large number of wild goldfish, their natural prey. I kept a few snakeheads with catfish (Pseudobagrus fulvidraco) back then, but I didn't notice any aggression toward the catfish.
An observation about the red snakehead (Channa micropeltes): people have noticed that this fish frequently takes air from the surface into it's mouth - I think possibly that air is held as a bubble in the snakehead's head between it's eyes and it's snout, to provide buoyancy and balance the weight of the fish's head. If one examines an image of this snakehead, it appears that the fish's head is rather long and possibly unbalanced. I also have been able to see the bubble siting up against the snakehead's roof of it's mouth. This is just a thought I have, but I am pretty certain there is some merit to the idea.
This fish is very tasty. I've very often caught it when I'm fishing because there are lots of them in Indonesia where I live. This fish is called Gabus in Indonesian language, which means liar - because they are good liars. They usually take a very close range to their prey and act as if they won't attack. They are good actors, and if their prey aren't careful, HUP! Yummy. This fish eats other fishes. As far as I know, there is another type of snakefish. I don't know the scientific name, but they are called Bloso fish, which means dumb. They're called so because these fish won't try to escape even when you're holding them with open hands. They just lie there like a deadfish and don't move!
All species of snakehead are illegal in the whole United States. Fines and penalties can be severe so if you live in the USA be careful when obtaining one from anyone.
Snakeheads are very hardy. Many years ago, I caught an 8 cm specimen from a pond and decided to keep it as a pet. Being a poor student, I fed it only when I had some spare cash to buy feeders. Despite the irregular diet, it still survived and grew to a size of 30 cm! Now the part that proves that this species is really hardy. One day when I got out of bed, I walked 2 steps and stepped on something slimy. I looked down and saw my pet under my feet. I quickly retrieved it and threw it back into the tank. Before that, I noticed that the fish was already quite dry, which meant that it was already out of the tank for quite a while. A few hours after it was back in the tank, it threw out everything it had eaten the day before and for the next few weeks, refused to eat anything. I was worried, but it was eventually unfounded, as it was back to normal after some time
I owned a Channa marulia and found that, while they will eat anything that fits into their large mouths, they are not nearly as aggressive as many people assume. As long as they are kept well fed and have enough space they will live happily with fish that are a quarter of their size.
Snakeheads have taken over local ponds and lakes in the USA and are eating the native species to extinction. Many American states have programs that buy this fish if caught while angling. They are believed to have been introduced by our fellow aquarium keepers after they have grown. :(
I'm an American living in Indonesia and am enjoying the amazingly low cost of the fish hobby here: custom-built 1000 liter tank $170, snakeheads $1 etc. My favorites are the Red (Giant) Snakehead for ferocity and the Ocellated Snakeheads for beauty. The Giants are formidable, at only 40 cm they'll quickly eat 10 frogs apiece, 15 cm long skinks, and catfish of 25 cm. They'll sort of nuzzle the catfish, then inhale the tail end, then chomp their way up the body leaving about 8 cm of head protruding. Then they go into the bulldog shake until the head of the catfish falls off. Anybody watching will back away from the aquarium and cover their mouth in shock. The ocellateds here are native to Sumatra and Kalimantan. I have two at about 33 cm apiece. They show a preference for smaller prey, especially shrimp, which also brings out their colors. The smaller ones (15 cm) are metallic blue or green with golden spots. These like to be fed cupfuls of guppies which we net from the nearby drainage ditches. About mixing fish...my second largest aquarium houses three Giants of 40 cm, a Silver Arowana of 55 cm, five Clown Knives of up to 55 cm, two 30 cm ocellateds, and a midsize alligator gar. They all get along, for the most part. The only casualty has been one of the Giant Snakeheads, killed by the biggest Clown Knife, the long-standing Tank Boss. So don't think you have to keep the Giant Snakeheads in isolation. I will say they are frighteningly fast and voracious eaters - they will always eat first, and the most as well. Other fish will only get a chance to eat *after*. Given their size, speed, and killing power, they are for me the most impressive freshwater predatory fish one can keep in a reasonably-sized tank.
I have kept 3 species of snakehead: Parachanna obscura, Channa gachua and currently Channa melasoma (which is very rare in the UK). I have found no need to feed live fish, as they have all taken whitebait, shrimp, cockles, etc with no problems! They are not all aggressive either! Mine have been kept with Africans, siamese tigers, bichirs, knifefish, oscars, fire eel and various catfish, but not all at the same time. If you have the right size tank and tankmates, they are very interesting to keep, just research each one individually.
These pages have enough comments to give the reader a basic idea on the topic. Further comments are still very welcome (through the site's contact form) as long as they provide new and/or advanced information not yet discussed in the existing ones.