Don't want to be mean, but hope you got larger tanks also setup at home, since with a Fire Eel, Gar, Fahaka and Snakehead all in the same 160G tank you will eventually have problems... as you said they are still young, but from experience i can tell you as a Fahaka gets older and starts taking up more area to feel comfortable, they can become quite aggressive to anyone that starts getting too close too often, or when they try and steal food from your puffer...
I remember when i stared seeing my fahaka stalking tank mates, i would literally be at the tank pointing at her telling her off till she sort of learned to not attack any tankmates if i was watching, but if there was food in the tank, or they started annoying her, she was not shy to let them know whether i was there or not...
So yeah, just be sure to keep an eye out on how she does as all of them grow coz i've even heard of Fahaka's living peacefully with a selection of tankmates for up to 10 years, and then suddenly one day decide to go on a murderous rampage killing everyone in the tank...
My idea is to move the gar and the snakehead to another tank in a few months. I think they will work better together in a tank whit a litte bit coolder water, and the fahaka with the eel with eachother. Think its a better combo and the fish would be more active and feel more free.
These fishes need spesial recuarierments, and i think its better too have them in a own tank, ore with not so many fish. Not because i am afraid too loose fish, but because when you have it in a own tank ore not with other mainfishes, you can spesialize the enviorments and water chemestriy 100% after the fish. The fish will be more happy, and you will have better control. So i would not recommed mixing these type of fishes, unless you got a giant tank and alot of time, but then again fahaka is tropical and channa is sub tropical. It was a litte "test" project, i am unlikeing the idea have so many Main fishes mixed, more and more for everyday that goes. So i maybe need start too look at some new tanks hehe, soo far its all good. But defenetliy not a loong term solution.
Sorry for bad gramma. I live in norway, not so often i use my english.