Note, I do not keep the larger fw species as most of my tanks have been too small. My largest fish are clown loaches in a 150gal.
Are we sure they are not Balas, Balantiocheilos melanopterus? If they are this, then
Given its potential size this species is clearly unsuitable for the general community aquarium. Though normally quite peaceful it will also eat very small fishes and can upset slow-moving or more timid tankmates with its constant activity and vigorous feeding behaviour.
It’s therefore only appropriate for very large tanks containing robust, similarly-sized tankmates that enjoy the same conditions. There are a number of suitable choices but recommendations include Hypsibarbus wetmorei, Barilius, Cyclocheilichthys, Osteochilus, Barbonymus, Mystacoleucus and larger Garra species.
Although it is gregarious by nature this is a shoaling rather than schooling species which develops a distinct pecking order and therefore should always be maintained in a group of five or more. If only two or three are purchased the subdominant fish may be bullied incessantly whereas solitary specimens can become aggressive towards similar-looking species.
If if is a Pangasianodon hypophthalmus, iridescent, then it will get over 4 feet long.
Unsuitable for all but the very largest tanks. It’s a very active open water species and tends to be skittish when kept in cramped conditions. This can lead to problems with the fish banging into the tank glass and items of decor, often resulting in injury. For even a single specimen to be housed long term a tank measuring at least 15′ x 6′ x 6′ (450cm x 180cm x 180cm) – 14,580 litres would be the minimum needed. Juveniles can of course be grown on in smaller tanks............
It’s a shoaling species by nature and will be less flighty when maintained in a group. Obviously a truly enormous tank would be needed to adequately house several.
Note this species is considered endangered.