Lima maxes out at 2', elongatus at 1'.
Check out this thread which includes a relevant piece from the genus revision:
http://www.monsterfishkeepers.com/f...elongatus-ID-thread&highlight=trigonocephalus
Here is a small write-up I made on lima/elongatus.
These are ambush predators that stay/float vertically, head down among vegetation pretending to be a twig or a plant and wait for a suitable prey to come by too close.
Young Sorubim species like the company of each other; adults don't care.
IME and IMO, the vast majority of people thinking they are buying a Sorubim lima are actually buying a Sorubim elongatus in the US, so chances are great that yours is S. elongatus, which tops out at 1', not 2' as S. lima does.
They are quite hard to tell apart from the exterior features for laymen like us:
http://www.planetcatfish.com/forum/viewtopic.php?f=13&t=30938&hilit=+elongatus (that's one of mine I was trying hard to ID). As you could see, our colleague Back (high level hobbyist) from Finland thinks the position of the mandibular barbels with respect to the gular and other skull features may be telling. I do not remember this approach having been validated by a known respected ichthyologist personally but I think the latest genus revision justifies this ID approach.
I've never seen a 2' one in person, not even one longer than 11"-12" TL, while I have owned and seen scores of them. Mine never grew beyond ~11", which makes me assume they were all elongatus but I have not had them long enough to be dead sure. For now, this leads me to believe that most/almost all we have in the US are elongatus. I have seen only 1 or 2 approximately two-footers on the photos originating from the USA here on MFK (here are some pics of an almost fully grown lima:
http://www.monsterfishkeepers.com/f...e-lima-shovelnose-catfish&highlight=elongatus ) and a few in between 1' and 2'. Our colleagues in Europe say they see 2'-ers sometimes, not that rarely.
The Cat-eLog entry for elongatus
http://www.planetcatfish.com/common/species.php?species_id=697offers kind of soft ID: "...Very generally, Sorubim with spots are usually S. elongatus. (TBTB edit: as opposed to the other 4 species in this genus; this appears mostly true IME with ~20 of these fish.) They are more of a black water species and, as with most such species, tend towards more variable, spotted patterning."
They need not live feedings, unless we are talking earth worms or ghost shrimp, lizards, land frogs, etc. They are small predators that snatch small fish (anything that can fit in their mouth which is relatively and surprisingly big for their slender body structure but not that big compared to other medium and large Pimelodidae catfish), crustaceans, insects in the wild. I always feed mine frozen/thawed foods - small whole fishes, fish pieces, shrimp/prawn/etc. or their pieces if too large (do not peel; raw is better than cooked), and sea foods.
They can be trained to take pellets but the cases where they thrive on pellets are very few it appears to me, even on Hikari Massivore pellets. I have never seen them fat and happy on pellets, rather always thin and slow-growing. Anyone, correct me, please, if your experience differs.
When small, mine like freeze-dried and fresh bloodworms, plankton (mini-shrimp-like creatures), etc.
The growth on elongatus is not fast, perhaps 6"-7" in one year starting from ~3". As you see my experience with lima is most likely zero, so IDK how fast they grow. The fact that they reach 2x larger adult size may or may not matter.
Check this excellent link:
http://www.seriouslyfish.com/species/sorubim-lima/ - the info is well written and arranged. In the notes it says: " (TBTB: S. lima is) Distinguished from S. elongatus by having modally 9 pectoral rays; 21 anal-fin rays; 16 gill rakers..." The page does not state the counts for elongatus anywhere. Neither have I found a species page for S. elongatus. Unless I am missing something, I find this odd and not as helpful as it could have been otherwise. All other pointers refer to things that are subjective. Nevertheless, I enjoyed reading the page and learned a lot.
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Pseudoplatystoma fasciatum I'm thinking i gona try. I must decide.
You can certainly try it, I'd think, esp. if you have a plan to either upgrade within 1-2 years or have someone qualified who can take your outgrown fish.
