for stonies like monties.....you want to use something like Kent Marine Tech D coral Dip mixed in a saltwater concentration or a lugols solution. Iodine seems to be effective (which both contain). I also used prazi pro to treat the outbreak and would get a ton of nudis falling off but I would use that only if an outbreak.
The biggest problems with MEN is that the eggs do not respond to treatment or dips always as they are the BIGGEST pain to kill, so if you have the eggs and just dip you might still be introducing it into your tank.
If you are going to keep corals or fish, you really might want to consider setting up a QT tank. I am not one to preach as I am REALLY bad about it, but now that I have been burned, I hope others can learn from my mistake. All you need for a QT tank is a small 10 gallon tank (depending on the fish if you get a tang you will need a longer tank), a heater and a sponge filter and a VERY CHEAP light.
The sponge you seed in your main sump for a couple weeks, then you fill the tank up with water..bare bottom, no sand, place a PVC pipe in for fish to hide in or if coral nothing, get the heat up and tank is ready to use. I take about 1/3 of the water from my main display and keep salinity about the same as main display....if you are not ready to add anything in..then you just have to place a couple pieces of food in tank to keep bacteria going. But then you just simply clean out tank and start over between QT's.
This way you can allow the eggs to hatch out on the monti, dip before you put in, keep it in for a couple weeks, and dip right before you put in your main tank. That is the safest way.
I have just been reading so much infestation about flatworms, redbugs, nudis, a pyramid snails that the more I am spending in corals the more I realize I need to do this,
For a lot of the soft corals, polyps, mushrooms, etc a freshwater dip is very effective. (stonies to, but very stressful on stonies I found out) Zoos I read can not handle Iodine...not sure just what I read.
But whatever type of dip you do, make sure you swish the coral around in the solution...it is amazing what you will see down at the bottom of the bucket!
Good luck. I am going to try montis again, just have to wait several months. One good thing about MEN is they only attack Monti!