Haven't been on here in ages but great to see a good sized one in captivity. I can confirm that the higher dissolved o2 would likely be preferred given a lot of their natural habitat is in rapids during their annual migration which should have high o2. I've caught them in slower moving rivers where there were tidal direction changes daily (50 miles inland from the coast) in Suriname and to date is probably the prettiest catfish I've caught! This one would have shattered the IGFA world record by over a foot and probably 20lbs if I had been on lighter line
It would seem that I've encountered for the first time that our dorado catfish has been refusing a slightly less familiar feed (fed only occasionally) for several weeks, which led it to attack the bala shark. Of course, I cannot refute an alternative explanation involving two mere coincidences - of the switch to a slightly new feed and my dialing back the elevated water hardness, and of the return to a more familiar feed and the end of the acclimation period to the lower water hardness. But two coincidences seems too much.