it's a good idea to return this to the shop as fast as you can!
both parents are able to reach 4 feet.
the Pseudoplatystoma fasciatum already is a catfish of respectable size; the Oxydoras niger can and does reach twice the weight and girth of an adult TSN
if you doubt this, well, here's a picture of both parental species taken by yours truly:
http://www.planetcatfish.com/catelog/im ... ge_id=3881
the little squirt on the left is a 3.5 foot TSN. the head of the niger is almost as large as my own.
the hose you see in the background is a 2" gardenpond hose, largest diameter available in the shop.
photo was taken at Verduijns.
given the fact that hybrids often grow faster and larger than both parental species -this is called hybrid vigor- you can easily end up with a 4-5 feet long catfish with the size of a baby bottlenose dolphin and the weight of a fully grown adult male German Shepherd dog......
not something you can keep in any normal sized home aquarium!