Rainbow Shark is missing

Hi everyone. Rather new to fishkeeping.

I have a 100 litre tank with very ornaments in. Gravel substrate.

Population:
15 x tiny guppies
1x neon tetra
1x pencil fish
2x corys
2x danios

2 days ago we added a "sucker fish" (I cannot remember its proper name. Has a long tail) as well as a rainbow shark. Shark is the problem child...

Shark loves to hide. We can never find it. And now, I haven't seen it all day. I am worried that we may have put the box filter on top of him yesterday by accident so tonight I picked it up, shook it around a bit, and then also gently shook around all of the other ornaments and stuff. This guy is nowhere!! I did see him this morning though so I'm thinking, if he died, surely his body wouldn't be decomposed already... and also, who would eat him?? He is the biggest guy in the tank.

Only thing I can think of now is that he burrowed under the gravel. Do they do that?

There is a lid on the tank. Box corner filter and also an under gravel filter. Stick heater (set to 25 degrees celsius to keep everyone happy).

 

I would check around the outside of the aquarium too, especially towards the back. Never know what may jump out.

 

I did check...the tank is a counter top, not much around. Unless he jumped far enough to land in the plugs and cables etc! Goodness.

 

Might be curled up inside an ornament. Fish are hide n seek champs.

 

Sneaky guy!!! And I looked in there. I now see he swims into the roof of this ornament and pretty much spends all day in there. That's why I couldn't find him.

 

Sneaky guy!!! And I looked in there. I now see he swims into the roof of this ornament and pretty much spends all day in there. That's why I couldn't find him.

Hide n seek champ

 

Good to hear it was just hiding

 

Crikey I was worried. Also a bit disappointed... he is the coolest and most expensive fish in the tank!