Disappearing Cardinal

[numbnuts70]

Pair of bangaii cardinals introduced last week . They seem pretty chilled as do the other inmates but now one is missing for 48hrs. No overflow and no other fish bigger than 3/4 CMS
Any ideas ??

 

[lapin]

dead under rockwork

Oh and howdy welcome

 

[Super Fly]

they are nocturnal and one may be hiding during daytime, try searching at night when lights are all off