IMO know the water total hardness / alkalinity before messing around with high doses of alum if fish are important. Hydrated lime may be needed with the alum when the pond has low or medium low and sometimes even a medium alkalinity concentration.
Jar Chemical test procedure.
1. Fill multiple identical jars with pond water.
2. Add a measured increment of flocculant (such as agricultural gypsum or alum) to each jar and stir thoroughly. For example:
1. Jar 1: 1 teaspoon of alum or gypsum
2. Jar 2: 1 teaspoon + 2 tablespoons of alum or gypsum
3. Jar 3: 1 teaspoon + 4 tablespoons of alum or gypsum
3. Wait 12-24 hours to see which mixture successfully clears the water and causes the clay to clump and settle at the bottom.
4. Calculate your pond's volume (length X width X average depth X 27,154 gallons per acre-foot) and scale up the dosage from the most successful
jar's water volume to treat the whole pond.
Bob Lusk says this
https://www.pondboss.com/news/inside-pond-boss/clearing-muddy-waterIf the pond has low alkalinity(hardness) then the alum does need to be buffered with hydrated lime so the water does not become too acidic and kills fish. See Bob Lusk’s info above.
Rainman on the Alum Kicks Clay Butt says this: For about 1.3 ace/ft of water, I'd suggest 100 pounds of alum and 50 pounds of hydrated lime. If it doesn't clear in 24 hours, add 50 more pounds of alum, Hy Lime could be optional on the 2nd application..
A 3/4 ac pond likely has more water in it than 1.3 ac ft of water!!! Amount of suspended clay in the water also affects the amount of alum needed to make the water clear.
IMPORTANT NOTE -- if the alum treatment does not make the water clear the turbidity was probably not caused by suspended clay.
See this thread for other options of cloudy water.
https://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=37851
