In case you get wels catfish in your pond, you don't need any pellets. This creature is a predator and it can easily eat fish, frogs and any other creatures.
Some basic facts about this fish:
1) grows fast (approx.):
1st year - 0,5 kg;
2nd year - 1kg;
3rd year - 2kg;
4th year - 4 kg;
5th year - 8 kg;
6th year - 16 kg;
12th year - 32 kg;
24th year - 64 kg;
This growth rate depends on forage base and different circumstances. Sure, there is difference between living in large river and small pond.
2) wels catfish can survive in water with low oxygen level;
3) it eats much, very much
4) very tasty fish with no scales and only one large fish bone (no small ones).
5) strong fish in case you like fishing.
6) they should be able to spawn in ponds too.
I've purchased some little ones last autumn and probably after some years I'll be able to get some big fish!