Help: indented tummy?

[vegansushi]

His tummy will go from indented to normal within a couple seconds. I've never seen this. Is he breathing funny?

He was in the fridge for two days because he has some gravel in his system, but he hasn't eaten in a while and I was getting concerned. Did I take him out of the fridge prematurely? Water parameters are normal and pH is around 7.6, temp around 62 but I might try to cool his tank down a lot more in the meantime. SOS ):

*these pictures are literally 10 seconds apart

 

[Calgarycoppers]

Thats from the food and gravel moving through his system its normal at this age to do that BUT the gravel is hugely concerning at this size. Feed fatty food small pieces of thawed raw salmon, cod or shrimp or repashy bottom scratcher or grub pie.