We will discuss the details of dosing and such for this type of application later in this writing.
Since PP comes in the form of a crystalline powder or flake, it is always weighed for dosing as opposed to measured by volume. These weights will be in grams for the purpose of this writing, so you will need an accurate gram scale to weigh it. The traditional beam/balance type scale works fine for this, but today there are also some very accurate, yet inexpensive electronic gram scales on the market. No matter the scale you use, just make sure it is accurate. PP is one chemical you do not want to overdose. In discussing a possible overdose, PP can be neutralized and deemed inactive with simple hydrogen peroxide. What this means, is if you add about ½ cup of peroxide to the system after any PP treatment (be it an overdose or not) it will deactivate the PP. So as you can see it is important to have the needed amount of peroxide on hand in the case of any possible problems, bad reactions, or overdoses. Simply add the peroxide and you will see the color change before your eyes and the water becomes clearer. You can also use the peroxide at the end of any treatments if you want to make certain that the PP is made inactive after the time frame you desire. Also, certain ammonia binders also deactivate PP as well. I do not recommend their use for this purpose however. The reason I mention it is because you cannot have any active ammonia binding agents in the system when attempting to treat with PP. If you did, the PP would be rendered inactive immediately, and you would not be able to maintain the proper color/PPM. We will discuss the color issue shortly and you will then understand why it is mentioned here.
As for dosing, we usually do this based on the PPM (parts per million) that will end up in the water initially. I say initially, because as soon as it mixes in the water it begins oxidizing anything organic in the water, and thus the active PPM reduces proportionately. I say active because the PPM you start with goes down proportionately as stated, and thus this leaves us with less and less active PPM. We will discuss this in detail shortly.
These organics I refer to include algae, fish waste, dead leaves, insects etc. As PP oxidizes these organics, it is expending itself proportionally as well. So what this means is that the more organics in the pond/system, the quicker the PP will get spent, and its killing/oxidizing power will decrease more rapidly. What this now means to us when treating fish for parasites is that the more energy it uses to oxidize these organics the less it has left to get to, and kill the targeted parasite. Now this translates into the basic fact that the dirtier the pond or system, the less effective it will be at killing the parasites/pathogens. This also means that you will most likely need multiple and consecutive treatments to do the job. The initial treatments will be expended quickly in cleaning/oxidizing the organics and each consecutive dose will therefore be a little more effective at getting to the parasites, as well as last a little longer each time. So with all this in mind, we need a way to figure out its effective strength or active PPM for the duration of each treatment. There are two basic ways to do this. One way is with the use of an ORP meter (Oxidation Reduction Potential Meter), and the other is simply by monitoring the color of the water after the application of the PP. For the purpose of this writing, we will solely discuss how to do this based on the color of the water, as this is much more practical for the average person. Use of an ORP meter is a little more advanced, and we will discuss this in another writing.
PP can be dosed from 1 PPM to 6 PPM for treating fish generally, but here at the farm we use three primary doses for three specific reasons. These are 1 to 2PPM for routine cleaning of systems and filters, and 3PPM to 6PPm for treating parasites. I very seldom use doses higher than 4PPM however, and I would highly suggest the average hobbyist never use any higher than 4 PPM doses for treating parasites. I would even suggest you stick with no higher than 2 or 3 PPM treatments until you get some experience with it.
Now, to figure out how much PP we need by weight to achieve a given PPM is not difficult. One way is to go to click2roark.com. This is a website by hosted by one of the greats in the Koi treatment world. In real life he is a lawyer, yet he also has an extensive knowledge of chemistry, and Koi health in general. He is also a very funny guy whom I respect immensely. On his website he has some very good chemical calculators where you simply input the gallons to be treated, the desired PPM, and it will give you the exact dosage you need. As well, it will give you these doses in many forms of measurement, such as grams, pounds, ounces, etc. It is a very handy tool, and I can’t say enough good things about these calculators.