It's a true tig. Brachyplatystoma tigrinum aka tigrinus catfish. $200 is not bad, nowadays if you look harder can score one for $150-$125 before shipping. A small one 2"-3".
I am afraid 125 gal won't be enough for life, which can last 15-20 years. They will reach 2' in under 5 years with proper care. Been known to reach 2.5'-3'.