I don’t think there are many keepers with Asian redtail cats over 30”. Largest I have kept reached 2ft and my most recent attempt failed as my 26” Wykii took a disliking and killed the Asian rtc’s.
I think they are somewhat of a mis understood fish. You can get them to co habit with tank mates if the tank is large and the tank mates are too large to be eaten. You will struggle to raise more than one with any other hemibagrus. The three 8” ones I have currently were part of a trial and have all had to be separated.
Feeding is easy in an established tank with other fish and they put on weight well, however if you do end up keeping solo fish they tend to sulk, hide and go on hunger strikes.
Up to 12-14” you may get away with one in a 6x2x2 with other large tank mates but as they get to that size the tank will not be big enough for their territory so more problems could start. My Wykii was fine solo in a 6x2x2 up to 16” and I would suggest at that point any larger hemibagrus needs a pond or very large tank. In my opinion an 8x3 would house an Asian redtail for “life” or at least 10 years of it due to their nature of staying put under their cave and venturing very little. Note however that they have a strong habit of redecorating, so everything has to be very sturdy. Ideally a pond though. With a happy one I think 2 years from 3” to 16” and a further 3-4 years to 24” then things slow down
