three striped damsel

So I have a 32 biocube and a 16 biocube. I bought the 16 specifically for my four stripe damsel. He’s my oldest (and currently only after the passing of my 10-12 year old engineer goby) fish. I want new fish for my dt but he’s a turd biscuit so I’m planning to put him in my 16. Is that big...

My damsel is doing a strange behavior I've never seen before. It's rubbing its belly along the corner of my tank, away from all the other fish. Usually he's in the thick of it with the clowns. But today all he seems to be interested in is going up and down the corner, and barely showed any...