Great photo you've found!
What's their growth rate and in a year, how big can it grow?
*****Slow, perhaps 0.5"-1" a month in the first year.
I know these cat can be quite skittish but my tank have plenty of driftwood so, there's place for it to hide.
*****It is indeed one of the most skittish. Bolts at sudden move, light, sound, anything unusual (like food dropping in the tank), etc. and hits everything in the way. It doesn't hide but it should feel more secure with much cover around, I suppose.
And does it true that when it grows older, the silver sheen gone? Or it can grow like in the picture..
*****As Moe started saying, we have seen only a handful of them grown over 1' on MFK over all these years, it seems. To me, this implies they are very hard to raise to a large size. I myself have lost 5 or 6 already trying, 2 lost to predation by a tank mate, 3 to an unknown disease. Got two left currently at 5".
From the very little we have seen, those at 1'-2' look the same metallic awesome color as the juvies. Larger ones, IDK. Your photo implies the big guys lose it largely except the head but a fish can change its color when caught and pulled out of the water.