Liearus eating clams in their shells

[CFC]

I've recently started feeding my rays whole clams in their shell, more to give them something more interesting at meal times than cooked and peeled prawns or whitebait than anything else. The trouble is they share a tank with a 20" Liearius pictus which has decided it likes the clams too, it swallows the whole thing shells as well and then spits the empty shells back out a couple of days later.
There doesnt seem to be any bad side affects from this, the first time it happened i was a bit worried but once the shells reapeared and there was no visable damage to the fish i felt better about it.

Would large catfish such as these eat hard shelled molluscs as part of their wild diet and then eject the shells once the meat has been digested or is this something i should stop before something goes wrong? The Leiarus also eats whole apple snails (also intended for the rays)but appears to digest the shells or at least grind them to powder so they are ejcted in the more normal manner but i have found no information that says these catfish would usually prey on these food items.

[racoll]

I would have thought they would eat that kind of food in the wild, but i don't have any facts to back that up.

[Silurus]

There are molluscivorous catfishes whose sole diet are whole clams that are wholly digested except for the shell (the pangasiid Helicophagus is a good example). However, in the case of Helicophagus, they have a very distensible anus which allows them to pass out large shells through it.

[CFC]

Do you think it could damage my Liearus or is it safe to just continue feeding the clams?

[Silurus]

If the fish isn't showing any distress, I'd leave it be.

[CFC]

Great stuff, the rays have been really enjoying getting into the clams and i felt a bit bad about not feeding them to them any more if it was going to cause possible harm to the Liearius, and i'm sure they all benefit from having a wider range of foods offered. Thanks