Well I don't know my cichlids real well but I would venture to say the severum would be an issue. I have heard they are docile as far as cichlids go but I would bet he would mess with a similar sized silvery fish. I have a blood parrot and he messes with a similar sized bala quite a bit and blood parrots might be the calmest of the cichlids. Clown loaches are fine unless ridiculously small, things tend to ignore these guys it seems. Leopard ctenopoma, I fear for it's safety from all these fish, it will die for sure. Ghost knife could also be an issue, may be fine if they grow up together. I'm not sure if they get more agressive with age but they seem fairly lax. Fire eel could definiley eat him. If they were in a monster tank and the hujeta could acheive it's 26"
or so potential and fire eel at 36" it would be fine. It seeems fire eels still grow quite large in restrictive space but hujeta do not and may stay 9-12" while the fire could be 30" in the same tank. Hujeta are very skittish and I fear putting them with my blood parrot and they suicide nose bonking the glass. This combo would take an enormous tank anyway, 250g bare minimum. Without the fire eel smaller tank would do. I'm not an expert so experiment if you must, Good Luck!