most of the points have been covered here.
but i will stress we have a habit of labeling things as hard to keep or die easy etc etc. i have spoken to a few keepers over here who and i will hold my hand up as one and say goonch are hardier than we give them credit for. but the setup is the key. if you move something in the tank they stop feeding move something outside the tank they stop feeding. now to the uneducated or people who haven't done research this cause owner stress, you keep trying to feed but they refuse you miss a few bits of food and its start to turn the water etc etc. but if you are accustomed to this types of things and can read the signs of when it's hunting then you can choose when to try feeding it. over winter mine didn't eat for nearly 4 months no stress to me because i understood why.
i also think there is some big different between the care of young fish to larger fish and this is partially to do with young fish staying to the shallows/ pools and the water temp being more fluctuating and the oxygen levels the same. whereas larger fish need colder temps and higher oxygen levels due to the fast flow and deeper water of the rivers they occupy but i'm guessing this. it may be the reason young fish seem fine in a tropical tank with cichlids etc then they die as they get bigger in the same conditions
moving a larger fish may prove more difficult to a young fish because of this, but with all the great advice above you won't go wrong
my next point would be water conditions. everything i have read say you need pristine water. i dont totally agree but then we should strive for the best all the time. for the last few months my tank has had a 15% change once a month (bear in mind it hasn't feed) it has 5 internal filters for current and filtration nothing special just sponges in there in fact the fish cost me more than my entire set up. is my water perfect? well there are no signs to it not being hahaha (just to confirm i ran a thin line on water temps if i had done my normal weekly 25% changes over this time i ran the risk of dropping the temp too low for it to regain). i run regular water tests and they always come through fine, are we over complicating things???
last point
if 20 people buy a large fish that has never been kept and 15 die is it now a difficult fish?? where as if 20,000 people go out and buy guppies and 15,000 die does it get the same reaction??
