simple... quite a number of wild fishes comes with dieases, some which we dont even understand. most tank bred fishes especially the 2nd or 3rd generation will have stronger immune system to local conditions.
but the most important thing is will wild fishes survive their new surroundings in a tank? a really big risk to take for an expensive fish. after all we cant compare ourselves to jack watley..hahaha

ie ...wild angel fish is known to be diease infested, mix with local fish ie the clown loach...u will end up with all sort of problems... local fishes have no immune system to fight foreign dieases

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