I am afraid to put a even a soft number on it. Yes, they grow much slower than large Pims, perhaps 2-5+ times slower. Huge range, poor guidance, I know, but that's my best "guesstimate".
Do we know if it is w/c or farmed? There is this notion that some farmed ones, such as Hemibagrus nemurus (most often albino), IDS, etc., are poor growers, which I don't understand as this would ruin the food fish farming business... but, indeed, we have been seeing fishes of abnormally slow growth and attaining much smaller adult sizes, it would seem of both hemibagrus and the IDS. Supposedly due to insufficient attention of the farmers to the maintenance of a healthy gene pool.
The usual thought/conviction is that we in the trade get a tiny % of the fish raised for food.
This conundrum could be reconciled by a supposition that the ornamental fish trade is now getting supplied from a different source than food fish farms and the ornamental fish trade may even benefit from smaller fishes as more hobbyists can house them. They would also benefit as these fish would reproduce poorly too (and are more sickly). All this increases the "ornamental farmers" consumer demand and farmers' security. ATM, this is but my wild thoughts, unsupported by anything.
It also depends on what housing mindset you follow, the ~4Lx2L min or some other.
Sorry. Wishy-washy. Lots of words, little benefit.
My two bigger wyckiis were ~14"-16" and in 1-2 years I have not noticed them to grow much. You may have more time than you think. ARTC I have no 1sthand experience with.
