We have recently introduced a bunch of new fish into the 25K, where wels lives. Four vulture catfish, 22-26", six giraffe catfish, 20"-30", two knives, 22" and 26", and Wallagonia leerii, 30". A peer from France, who makes great fish posters, commented, so I'll copy and paste it here:
nicolas florencio hello, I would like to have a feedback on the behavior of the wels catfish vs wallago Attu. because i have a friend who had a flathead catfish and his wels catfish killed him In europe the silurus glanis is the biggest predator, it still hasn't eaten any other fish in the pond?
Fish Story, a DIY Public Aquarium & Fish Rescue Thank you. Ours is not an attu. This is Wallagonia leerii or micropogon. The leerii suffered non-serious damage in the first day or two, supposedly from the wels catfish. It had healed up quickly and no more damage has been observed since. Leerii is a timid fish, at least IME, the ones we have had were not aggressive by any means, they don't appear to have and defend any territory, which is logical as they often stay mid water. Bottom-dwelling flathead catfish I have never kept but reading tells us they are aggressive, territorial, and will attack and defend their perceived space. Not too surprising an outcome if your friend's wels was far bigger than a flathead, that the flathead got killed. In terms of predation... Our wels hasn't manifested so far any interest in the smaller tank mates. We monitor this closely, rest assured. The smallest koi in there is a show quality platinum ogon bought little for $300, currently at 14", easily swallowable by the wels. It's been in the 25K for 2 months. No problem. There are also tinfoil barbs and bala sharks, some of which are well under a foot. All has been well. Doesn't mean it can't change overnight. We watch.
I'll note that one of the vultures also was bitten on the head/snout early on upon the introduction but not too seriously and recovered fine over a couple weeks. I too suspect Mr. Wels. No other problems have been noted yet.
