Update Aug 29, 2018.
The bigger GATF from the original Wes' batch of six are now down to two. Two more have killed themselves, despite having more calm tank mates than water in their 240 gal. So this is not a way to go.
With ATF it is survival of the fittest in the wild and of the calmest in captivity. No news though. Just like Wes
fugupuff
says,
-- keep them in a tiny tank, where they can't pick up too much speed, or,
-- in a tank with padded sides and top, or
-- in a pond, or
-- the best is from the get-go place them in their final home of tens of thousands of gallons, or
-- at the very least one ATF per fish tank but the last approach is the least effective, I think.
I have rehomed the surviving duo (the smallest of the six BTW, ~9" and ~10") to a different 240 gal to join the batch of the other, younger ATF, and installed two thick filter mats at the side walls of the tank (8'x2'x2'). Wes recommends padding the top too, perhaps by stretching a net, which is not easy to accomplish but I need to think hard how to accomplish that in the 240 gal.
Out of the younger batch of 4-5 VATF and 10 GATF, 3 more GATF committed suicide over the last 6 months or so. Not a single VATF. All GATF. And all were the largest in the batch (again!).
All in all, we now have
-- two 20" VATF in a 4500 gal,
-- one 14" VATF in a 240 gal, and
-- four to five 5"-7" VATF and
-- ten 5"-10" GATF in the 240 gal with the padded sides.
Below are the photos of the two perished GATF, final sizes 11" and 12", grown in 1.5 years from ~3", not the fast growing kind at all that some report occurs seldom (never mind the VATF on the top as its drama is described in our VATF thread):