Skinny fish, any thoughts?

[Nordlys Fish Room]

8 second video - fish in question is roughly centered in the frame

Sorry for the iCloud link but For some reason I got an error message when I tried to attach a video from my phone. 
 

I picked these young black-banded sunfish up in early September.  This is the only one that has stayed thin and maybe even gotten worse as time passed.  I’ve treated with a couple rounds of ParaCleanse but there hasn’t been the recovery I was hoping for if it were normal tapeworms.
 

He does eat but only frozen food (the rest of the sunfish do take the Xtream nano pellets readily). In the video he has just eaten (I specifically target feed him) and his belly is full and you can see some of his siblings that are much thicker than him.  Yet he still stays skinnier than ever. Does anyone have any ideas?

 

tank parameters are:

temp: 69-70 F

ph: 7.6

nitrate: approx 25 ppm

[Native Keeper]

Sometimes you'll just have picky eaters in the group. I don't know much about Black banded Sunfish, but if you can, I would recommend setting him up his own tank, that way it'll be easier to feed him, and he won't have competition at feeding time.

[Colu]

If he's eating ok and still losing weight it could be wasting disease you want to treat with Fritz Expel p active ingredient is levamisole or fish aid fish fenbendazole in food 

Edited December 30, 2021 by Colu

[Nordlys Fish Room]

On 12/30/2021 at 9:53 AM, Colu said:

If he's eating ok and still losing weight it could be wasting disease you want to treat with Fritz Expel p active ingredient is levamisole or fish aid fish fenbendazole in food 

I have been considering a more aggressive dewormer. He’s picky but I have been able to directly feed him with tweezers so I know he’s eating.

[quikv6]

Have you added the Expel-P or Fenbendazole to the food? That would be the best method to treat with those meds. From what I have read, Fenbendazole won't be effective in the water column alone. You could also try Flubendazole if the fish isn't eating, or trying to eat, but spitting it out.

I have not tried Fenbendazole, but have had good success with Flubendazole, or Levamisole specifically in the food.

Edited January 2, 2022 by quikv6

[Nordlys Fish Room]

@Colu I did try some of that Expel P a couple weeks ago. The progress is slow but the fish is putting on weight now. Still boney but the hard edges are softening and I think he’s growing a bit. That one probably just needed multiple types of dewormer to flush him clean. 
 

Update video via iCloud link