i have a clown with an internal parasite. it is called Spironucleus parasite.
The treatment is metronidazole which is in Bayer -Clont vet prescribed tablets. You need a tablet, i am going to crush it up, add a little water, thaw out some blood worms, put separated bloodworms in with watery tablet & freeze again. then feed to clown loach as a bloodworm cube. should work. in the mean time, separate them & feed them up on blood worms etc.