The care requirements for the various Macrognathus and Mastacembelus species are basically the same for the most part (aside from Mastacembelus ellipsifer needing a higher pH, and the larger species like M. armatus and M. erythrotaenia needing much larger tanks).
They often don't take well to processed foods (i.e. pellets) and almost always prefer raw foods like worms, shrimp/krill, fish, etc.. They like to burrow, so sand or very fine gravel will be appreciated, though you'll want to make sure your substrate doesn't have sharp edges. They need to have plenty of hiding places, especially if you're planning on keeping multiple specimens together.
I've never heard of an M. zebrinus reaching 18 inches in captivity. You usually see them hitting about 12" max. Borneo Python Eels on the other hand will hit 20", possibly up to 24".
