I have a group of Australian salmon tail catfish (arius graeffei) that are almost constantly active. There are more of a middle dweller though over a bottom dweller although they do rest on the bottom every now and then.
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Salmon tailed cats are my favourite catfish. Being in Australia I used to catch them when I went fishing and take them home and put them in a tank. Like pictus cats they like to be in groups of at least 3, and the more there are the more active they are. However be aware that there are several different varieties of them that are incredibly difficult to tell apart, the largest of the varieties grows in excess of 4ft, and the smallest tops out around 30-40cm, and are the one you are most likely to encounter in the hobby. The happier they are, the darker they'll be, ideal coloration being black on the top and sides and bright white or silver underneath. There is also a black and white piebald version, which I have only seen very occasionally, so I presume it is quite rare. Interestingly enough the piebald version is naturally occurring in the wild, I have seen a bloke catch one while fishing for barramundi. In the wild they (salmon tailed cats) share quite a bit of their habitats with saratoga (an Australian species of aro), so they will go quite well with yours. In my experience they grow quite slowly. They get very tame and personable, I was almost able to handfeed my WC salmontails. They are not in the least aggressive to fish that are too big to be prey (they are a predatory catfish and will chase and eat fish small enough to fit in their mouths), they are extremely peaceful, but can handle aggression from other fish very well, as they share river systems with rays and sharks in the salt, and barramundi, giant gar and the extremely aggressive and cichlid-like sooty grunter. Oh and crocs
. I highly recommend getting a trio or more of salmon tailed catfish. They are pretty close to being the best fish I have ever kept. They tend to roam the lower and mid water sections, but if used to it, they may dart to the surface for food.