My suggestion for a cichlid only tank would be to do a large 75% water change and substrate vacuuming, this is important to remove as many of the Theronts as possible from the system. Theronts are the free swimming stage of the parasite and the stage that is vulnerable to the salt/medications. Increasing the temperature speeds up the life cycle and allowing treatments to kill the theronts before they find a host fish and burrow into the skin.
After you’ve completed the water change and substrate vacuuming increase the temperature to 87 degrees. Dose the tank with 2 tablespoons of salt per 5 gallons of water, in a 150 gallon tank this is 60 tablespoons of salt. (This is for non-salt sensitive fish such as cichlids). You should also increase aeration by either using an additional air stone or adjusting the out flow of the filter to break the surface of the water or lowering the water level slightly for an HOB type filter so it splashes into the tank any of these methods will increase aeration during treatment.
In 3 days do a 50% water change and substrate vacuuming and re-dose the water at 1 tablespoon per 5 gallons of water so for the 75 gallons you just changed use 15 tablespoons of salt. In another three days do the same thing, 50% water change substrate vacuuming and add 15 tablespoons of salt. This should do it. In three days do another 50% water change substrate vacuuming with no additional salt added but keep the temperature elevated. In another three days do the last 50% water change and substrate vacuuming. Return the temperature setting back to where you normally keep it and the ich should be gone.
I don’t think this will be necessary but just as an FYI after the 1st 50% water change you can dose the tank with half a dose of Malachite Green as long as you don’t have any fish that would be sensitive to it. If you choose to use it make sure there is no carbon in the tank and you wait at least 30 mins after adding any decloranator to the tank as it will render it ineffective. If you follow my instructions above you should need nothing other than salt & heat. Only use once if you are going to use it at all.
Treating with salt and heat is a process that needs to be followed to be at it’s most effective. You can not just add salt once and forget about as it will in most cases as you noted just end up coming back if you don’t kill it during the Theront stage. This is why water changes & substrate vacuuming is such an important part of the treatment.
Hope this helps if you have any questions please ask.
