Prevention next time will work, not in this case as its existing and recurring.
The case still seems mild so salt should work. That being said, the protozoa doubles every time it splits so dilution helps to reduce the amount of protoza in the tank available to infect the fish.
Salt is the recommend treatment for mild cases at a dosage of 15-20g for each liter for 10 minutes or until the fish roll over...
Jinks recommendation is right on the money. I think the salt dip in the first incidence helped tremendously.
Salt dips are pretty scary, though, and you must not leave the fish unattended. The fish recovers very quickly when put back in fresh water.
Fishkeepers that are experienced in salt dips will leave the fish in after it rolls for a period of time that varies, but that's pretty scary.
A 3% dip is common, but you can do a 2% dip which is less dramatic and would be effective and I think Jinks' formula would be 2%..
I think I remember that you have aquarium salt, or rock salt. It comes out different than fine grain table salt, which is OK to use to, but here's the figures using rock salt.
Approximates because it's hard to get a level teaspoon with aquarium or rock salt.
Here are some percentages of salt solution:
How much (how little) is 1 level teaspoon per gallon?
1 teaspoon = .13% of a gallon
2 teaspoons = .26% of a gallon
3 teaspoons = .39% of a gallon - also = 1 tablespoon
4 teaspoons = .52% of a gallon
8 teaspoons = 1.04% of a gallon
So it takes 24 teaspoons of salt per gallon to make a 3% medicinal saltwater dip solution.
There are approximately 770 teaspoons of water in a gallon.
Or 3 US gallons of water in a 5 gallon bucket would take 14 tablespoons of salt to get an approximate 2% solution.
Make sure the salt is fully dissolved and the temp is matched with the tank, of course.
Here's a treatment protocol from the site: Seymour Aquariums:
If the fish are fairly strong, a good treatment is to try a 3% salt dip. Keep the fish in the salt solution until they roll over, then put them back in the tank. For alternative treatment, and less stress for your fish, try a salt solution of 1% and let the fish swim in it for 10-15 minutes, then place the fish back into the tank.
The parasites will also die off in the tank (with no fish) if they are left that way for 5 days. You must still treat your fish! Quick Cure works well for this issue. Quick Cure Directions: 3% salt dip, then administer Quick Cure for 3 days, doing 30% water changes each day before adding more medication.
That was a ton of information on the use of salt.
Another option would be to consider the following product by Kordon, if you want to forgo salt dips as a treatment.
QUICK CURE
*Quick Cure (4 oz. Treats 2,000 gallons)- $3.99
*Quick Cure (.75 oz Treats 360 gallons) - $1.99
*Quick Cure 32 oz. has been discontinued by the manufacturer
Effectively treats:
• Ich
• Velvet
• Gasping for Air
• Flicking against Rocks
• Protozoan Parasites
• Mild Fluke outbreaks
• Costia
• Chilodonella
• Trichodina
INGREDIENTS:
Malachite Green, Formalin
More Information for Quick Cure:
Directions; Shake well before using. Remove and discard all carbon from filter, but DO NOT discontinue filtration. Typically cures ich in 24 hours, treatment can be repeated in 24-48 hours, if necessary. If fish experience stress, change 50% of the water. Sometimes treatment will take 10 days to fully irradiate infestations. Replace carbon 2 hours after treatment. Quick Cure will temporarily change water color to blue.
Dosing Chart:
1 ml treats 18 gallons (68 liters)
I teaspoon treats 90 gallons (340 liters)
1 capful treats 250 gallons (950 liters)
1 fluid oz. Treats 500 gallons (1900 liters)
For Tetras or other delicate fish such as loaches, treat half dose.
I hope this helps, though I kind of bombarded ya with info.