PP can be used for a number of reasons, but is mainly used for nuking critters.
I would recommend using gloves when handling pp, as it is carcenogenic.
You will need an accurate pair of scales, a kettle and a bucket or jug.
Dosage for parasites is generally 1.5g per 220 gallons.
You MUST know your exact pond gallonage, overdosing can be fatal, underdosing is useless.
Do not use with Sturgeon.
PP reduces oxygen levels, so always ensure that the pond is well aerated.
Measure out the correct dosage for your pond and mix with about half a litre of boiling water. Most people then just stir it up and lob it into the pond, but you SHOULD let it gas off for about 10-15 minutes first. Half fill a watering can with pond water, add the pp mix and pour across the pond over a period of twenty minutes. Again, some peeps lob it straight it, but this hits the koi very quickly, it's like farting in a lift.
NEVER start treating the pond at night or when you cannot tend the pond. The pp should stay purple for about 4 hours and NO LONGER. If it goes over 4 hours then neutralise it with Hydrogen Peroxide. The pp will zap the organics in the pond, so if your pond has, for example, blanketweed, then it may turn brown after a couple of hours. If this is the case, add another 0.5g per 220 gallons and bring it back to purple.
Do not maintain the purple water colour for more than 4 hours!!!!!!
Some hobbyists use pp as a maintenance tool. Dosage for this is 0.5g per 220 gallons, on a monthly basis.
PP Baths -------- If anyone would like these procedures explained, please send me a pm.