Hi Rudmin. Although the pic is a bit blurry, I have to agree on the spotted Raphael [or Talking] catfish. I have a 7" striped, and a 5" spotted myself. They are very... very shy. If he is trying to hide behind the filter tube, he is probably a little stressed-out. I built 2 DIY caves for mine out of 3" PVC pipe/silicone and pebbles, and they both claimed one each for a home and seem very happy in them.