The Iridescent Catfish is a great species to have in nearly any large tank. The only problem I came across while raising mine is their tendency to eat smaller fish. Yes, it's true, I had seven Neon Tetras and an Iridescent Catfish along with some other community fish, and within a week, two of my Tetras had disappeared. I thought about what would eat them, and I could only come up with the catfish doing the dirty work. I staked out the aquarium, and sure enough, my catfish sucked those Neon Tetra right up. So I simply suggest not getting any fish that the Iridescent Catfish could swallow whole, since that's what it does.
My Iridescent is starting to go blind as they tend to, and the baby Bala Shark helps him all around the tank like a blind guide fish. My Iridescent goes from beautiful black to light, almost white in color. But watching this guy eat is amazing. He gets towed along by the little Bala and swallows big flakes whole. It's almost like a vacuum.
I bought my first Irridescent a little over a year ago. I soon purchased another because I read that they do better with more than one. They were only 5-7 cm long then, and now are 23-25 cm. When smaller they would often play dead. I even went as far as scooping one up, thinking he was dead, but then off he swam (frantically). They would always hide in a cave. I couldn't understand this, reading that they should be very active fish. They were very easily startled and would often go into a spazz attack,bouncing off the glass walls, rocks, anything that got in their way, making a complete mess of the aquarium, and often cutting their mouth or getting scratched. As they started to get bigger, I had to remove most of the rocks and plants from the aquarium so they'd have room to swim. By taking away their cave they then became active swimmers. They seemed to be very picky eaters at first, only eating sinking tablets. But now they love shrimp pellets and shredded cooked shrimp. They love to do bubble flips. Both of my Irridescents have "bold" spots on the top of their heads from hitting the class hood when getting too carried away with a bubble flip. I've lowered the water level, but that didn't matter. They still hit the glass almost every time. Like a dolphin jumping out of the water. They're a really beautiful fish. Mine are quite hardy. But they're not a fish for everyone.
Although they will over time become more active during the day, for some weird reason they like the dark. So you should keep the light off for about 1 or 2 days, then slowly work back up to your old light schedule. By then it will adapt and feel more comfortable. They seem to faint when they are scared, so if you find it lying on the ground upside down or on its side, don't worry too soon. Just wait about half an hour and if it isn't up then you should worry. I wouldn't recommend keeping this fish though, because they grow so fast. By within a year they will out grow even a 120 L if treated properly. They take up so much space and they scare other fish smaller than them. So you should be careful with these fish. If you have a 400 liter tank then you would be set. But these fish can grow up to 1 meter in length.
I used to have one of these guys but every time something freaked him out he would jet and knock himself out by running smack right into the walls of the tank. I couldn't bare to watch him knock himself out anymore. Just way way WAY too nervous a fish, and from what I understand they get HUGE. I bought mine at about 5 cm and he grew to 12 cm in a matter of a few months. I hope he has a better home now. It seems a crime they would sell these fish to unsuspecting fish keepers such as ourselves. They probably wouldn't knock themselves out if they had enough room to jet when nervous. My 60 L wasn't enough, and I highly doubt my 150 L would be either.
I have thought for a long time that Iridescent Sharks are completely unsuitable for home aquariums and should not be sold in pet stores or any LFS. I'm glad to find others who also feel the same way.