This is what's recommended for treating shell rot, it can be used for treating external parasites, too:
"1.) Grab a set of scales and measure out 35 grams of salt.
2.) If you don't have micro scales a good teaspoon is around 4.7grams, so 7 nice teaspoons will do.
3.) I don't mind what salt you use, personally I prefer pool salt.
4.) Throw that in 250ml of boiling water and stir in until dissolved.
5.) Then take 750ml of water from your crayfish's tank put it in a 4 litre ice cream container or something similar with high sides.
6.) Add the dissolved salt solution to it and stir again.
7.) Drop an air stone to keep the water nice an aerated.
8.) Set up an alarm clock/timer to 10 minutes.
9.) Drop your crayfish in and make sure it can not escape.
10.) Go do some maintenance on the tank.
11.) Come back and remove your crayfish when the alarm goes off.
12.) Repeat every 3 days as needed until next moult or lesions are "bleached out".
Except instead of repeating until the shell rot is bleached out, you repeating until you no longer see any parasites. Just remember you'll need to be fastidious about cleaning the tank, too, as some types of "worms" will be in the decor, substrate, etc and come back to the crayfish even after treatment (you could probably raise the salinity level of your tank in the short run to help, too, similar to what you would do for "ich" I believe).
"1.) Grab a set of scales and measure out 35 grams of salt.
2.) If you don't have micro scales a good teaspoon is around 4.7grams, so 7 nice teaspoons will do.
3.) I don't mind what salt you use, personally I prefer pool salt.
4.) Throw that in 250ml of boiling water and stir in until dissolved.
5.) Then take 750ml of water from your crayfish's tank put it in a 4 litre ice cream container or something similar with high sides.
6.) Add the dissolved salt solution to it and stir again.
7.) Drop an air stone to keep the water nice an aerated.
8.) Set up an alarm clock/timer to 10 minutes.
9.) Drop your crayfish in and make sure it can not escape.
10.) Go do some maintenance on the tank.
11.) Come back and remove your crayfish when the alarm goes off.
12.) Repeat every 3 days as needed until next moult or lesions are "bleached out".
Except instead of repeating until the shell rot is bleached out, you repeating until you no longer see any parasites. Just remember you'll need to be fastidious about cleaning the tank, too, as some types of "worms" will be in the decor, substrate, etc and come back to the crayfish even after treatment (you could probably raise the salinity level of your tank in the short run to help, too, similar to what you would do for "ich" I believe).
