Asian Sun Catfish Help

[Tomegoodwin]

I've had my asian sun catfish for a few weeks now. I never saw it though then read that these fish are happiest in dark places and hiding due to being nocturnal. However today I decided to take all my gravel out and go with sand.I put all my decode back in (bog wood 1side, slate caves the other side) all the fish are out and about all happy. Buy so is the catfish. It seems to find a hiding spot but then darts about the tank then hides in a new spot then darts around again. He's not stopped yet.it also swims under my acara sometimes as shown in the attached image. Any ideas what I could do for it?
Cheers guys

 

[BerryAttack]

your sun catfish will grow around 18inches. 
if your tank is not big enough for it in the future i would rehome it.

 

[Tomegoodwin]

I'll be getting a 6 door tank in the next couple of months
Not going to add any other fish just move what I have into the big tank