While activated sodium chlorite works great as a water purifier, it is a little more complicated than just how many drops are necessary.
You have to work backwards. After the proper contact time for the concentration you use, you want to have a little less than 0.8 PPM left over.
The concentration you need depends on the quality of the water you are trying to purify. Also, water temperature and PH effect the treatment times.
When I am working with lake or stream water, I start out with 4 drops MMS , activated, in a liter of water. I measure the free ClO2 10 minutes after applying the solution and am looking for around 3 PPM. If the water has passed through a 1 micron filter, it should be ready to go in about 15 minutes, so I wait 30 minutes just to be sure. If the water is unfiltered, the cryptosporidum take about 2 hours to kill off, so I wait 4 hours, just to be sure.
Bruce has indicated that with a 5% solution and using a 50% citric acid solution, 7 drops, activated, in 1 liter will give you a 10 PPM solution to start with. As the ClO2 purifies the water, the concentration drops because it is used up.
In the end, if you can smell ClO2, the concentration is probably above 1 PPM, and you need to add a little ascorbic acid to use up the residual ClO2.
Thank you Tom. I knew this would be an "it depends" answer; but I just needed a start. I did not think that 1 drop would be sufficient for anything but clean water. I also knew that sodium chlorite could disinfect a little on its own. So, your answer gives me the start that I need.
When traveling, I often encounter water that is harder than what I am used to. I find that 1 drop in a 1 liter bottle, activated, greatly improves the taste of the water, and also adds a little extra protection.
Yes, it will work, but there are a few things to keep in mind.
Fish are constantly adding waste to the water, and ClO2 is not long lasting. In industry, ClO2 is added to water to remove biofilm so it should be able to do that in a fish bowl as well, however, this is not a one shot deal. You would have to do a daily dose to keep on top of it.
Another thing to keep in mind is that fish, like people, are living things. If your concentration of ClO2 is too high, it will make them sick or kill them.
So now we are back to balancing a high enough dose to take care of the biofilm, but keeping it low enough that the fish don't get sick or die.
Bruce wanted me to pass on that if you use MMS in a fish tank you should use 1 ml of MMS and activate it with 1 ml of Hydrochloric Acid (not citric acid ), and this will treat 100 liters of water. You pour the mixture close to the filter.
He goes on to mention that ClO2 is not a scrubbing brush. It will kill algae, but not remove it.
I don't know why it is necessary to use a different activator, unless it has something to do with eliminating any residual. I have asked Bruce that question. If he answers back I will let you know what he says.