Floating/skinny Kuhli Loach

[Jaime]

I have had 6 Kuhli loaches in a 20 gallon for several months and they have all grown however one remained quite skinny. She started floating at the top and upside, struggling to get into the guppy grass to right herself. I have treated with dewormer, but it's been 4 days and now it seems she has given up and is just floating aimlessly at the top of the water, upside down, not hanging to the plants. Do you know what could be wrong? 

Edited October 27, 2020 by Jaime
missed info

[Irene]

Ah you're right, she may have parasites. I usually use Fritz ParaCleanse to treat for tapeworms, and if it doesn't solve it, then I try levamisole from selectaquatics.com to treat for roundworms. (Both dewormers usually require 2 treatments with a 2-week waiting period in between.) Given that she may have had worms for several months, not sure if it's too late for her but it's always worth a shot.