I took a look around for treatments for Lerneae. It used to be said there weren't any and manual removal was it. That is difficult and can case infections.
I found this: Dimilin, effective against Lernaea (anchor worm)
I found the below as well.
Treatment of Lernaeasis in Carps With Thunder: An OrganophosphateIqbal, Zafar
; Rani, Iffat
; Pervaiz, Khalid
. Pakistan Journal of Zoology; Lahore Vol. 44, Iss. 2,
Abstract.- The carps; Labeo rohita Hamilton, 1822, Catla catla Hamilton, 1822, Ctenopharyngodon idella
Valenciennes, 1844, Hypophthalmichthys molitrix Richardson, 1845 and Aristichthys nobilis Richardson, 1845 were
collected from earthen ponds reared under semi-intensive conditions. The parasitic examination of these fishes showed
that all fish species were infected with crustacean copepod parasite Lernaea cyprinacea and other Lernaea spp. C.
catla, L. rohita and C. idella had higher prevalence (62.5%, 68.75% and 76%, respectively) and mean intensity (12.1,
8.45 and 8.84 parasite/fish, respectively) compared to H. molitrix (9.1% and 3.0 parasite/fish). A locally available drug
“Thunder” an organophosphate (2, 2 dichlorovinyl dimethyl phosphate)
was used to treat lernaeasis in these fish
species. Three concentrations (0.10, 0.15 and 0.20ppm) of the Thunder were sprayed on the surface of the infected fish
ponds to eradicate lernaeasis. The 0.20ppm dose proved to be the most effective in controlling the infection, without
harming the fish. The water quality parameters remained in normal range and suitable for the fish after treatment
indicating that ‘Thunder’ has no harmful effects on water quality in fish pond.
Trying to find this stuff isn't so easy. I found this name "Dichlorvos
" This stuff looks to be nasty and I am not sure I would want to use it in any of my tanks. https://en.wikipedia.org/wiki/Dichlorvos