Probably not RARE but don't see that often...
This is my Purple Spotted Gudgeon. I was told it was a Purple spotted Goby/Gudgeon. When I bought it it about 1.5-2" long, and I was told it would get 3-3.5". Had heard of Gobies getting about that size and thought it would be a neat addition. Not a "Goby"...
Well a year later, it is about 6.5 inches long and 3" tall and a solid 2-2.5" wide, not what I thought. When it was bigger like 4" I did some checking and found out what I really had. lol He comes to the tank looking at me all the time wanting me to feed him. I say "he" but it is probably a female, though from the shape
Here is a pic of it when it was smaller with an Oto stuck in its mouth. I had to catch it and pull it out with a needle nose plier because the spines were stuck in his mouth. YIKES, was that scary for both of us!
Here is my Spotted Raphael Catfish. It was about .5" when I got it and the salesman said it was only going to get about 4". Then I couldn't remember what kind of fish it was for about a year.
I thought a number of times it was dying because it looks pine coned and then wouldn't move. Did numerous huge pwc for bettering the water quality.
One time and I went to fish it out thinking it was dead, moved it around with the net and it was wedged between the rocks and sort of got the net so I could get to it. It didn't move at all, rolled around like a log, then it darted away and hid. So not dead, lol Finally I kept searching until I found it's kind so I could learn about them.
They will suck up water or something to wedge themselves into spaces looking bloated and pine coned! But not ill.
They will stay resting for days on end, and only like to come out if the lights are off, eat and then sleep.
Here is the pic where it was not moving (playing dead) and I was changing it to a bigger tank it just stayed right there in front of the net while I ran to get my phone to take it's pic. Didn't even move until I scooped him up and plopped him in the new tank!!! Don't see him very often.