Does anybody feed their arowana with pork?

i have 3 silver arowana around 50 cm living 2gether and they eat like crazy. I cant afford if they keep eating like this n thinking of giving them pork as food, is this ok?

Or there is other option of cheaper food ?
Currently i m feeding them with salt water prawn bought from market. Can't afford to feed them with live fish/prawn/frog. But, still the prawn is expensive