Pond Boss Forums GENERAL QUESTIONS Muddy water alum treatment - hydrated lime needed?

New member here. read a lot of the threads (very helpful - thank you!), but never posted.

we have ~1/2 ac pond in central KS. Lots of clay soil. we re-graded the land and added rip/rap rock to the pond inlet a few years back -- most of the watershed channel now has vegetation and there's a lot of native grasses that have grown up over the rip/rap, so heavy rains don't typically mean a lot of clay runoff. In fact, the area where the runoff comes in will be crystal clear. until it mixes with the coffee soup mix of the rest of the pond water anyway.

current pond color is creamy-coffee. This morning we added ~210 lbs of alum (mixed/dissolved with water in 5 gal buckets and drove around in a jon boat dumping it in). Tested the pH after the alum treatment (with pool strip testers) - 6.5 - 6.8

do have an aerator that sits about 2' off the bottom. Turned it off just after we finished the alum treatment and plan to leave it off for a couple days.

couple questions:
1) enough alum? pond is somewhere between 8' and 10' at deepest, so I'd guess around 2 ac ft. of total water. I did add 50lbs or so a couple months ago before I realized you really need to do it all at once. don't know if that matters. Have another 100 lbs if we need to add more.

2) do we need to add hydrated lime? (have 100 lbs on hand) pH looks ok, and I do see a lot about fish kills with hydrated lime that seems worrisome.

3) if we do need to add it, safest way to add without killing fish? have bass, catfish, some perch, and a few grass carp (not many anymore - most try to leave when the pond overflows into our neighbor's pond)

when we finished the alum treatment I pulled two jars of water and added a pinch of lime to one of them. watching to see if it increases settling time. No real difference so far.(other than the jar sample pH readings anyway)

thoughts welcome! thanks

Ideally you should have done the jar test with alum and found how much was needed to clear the jar, then do the math to see how many pounds of alum you needed for the volume of water in your pond.

When I've done alum treatments with Rex Rains, the alum started to flocculate, grab the clay and precipitate to the bottom of the pond. If you don't see the alum flocculating, then I'd continue to add more, and keep testing pH. Alum will drop the pH, sometimes to dangerous amounts and the hydrated lime will raise the pH back.up.

We applied the hydrated lime first in bands across the pond, leaving 10-15 feet between the bands. Then applied the alum 90° across the bands of hydrated lime slurry. Flocculation started almost immediately.

Alum and hydrated lime were mixed in large tanks (not together in the same tank) and pumped out as the boat traversed the pond.

pH testing was done prior to applying anything and we tested during application. We didn't want the pH to vary more than 0.5 from initial reading.

thanks for the reply

see lots of floc as the alum is going in. It clears up after a bit, but there's no doubt where the alum 'trail' is as we were putting it in.

agree should have done the math before-hand. I was following the rules of thumb posted on this site and the Texas A&M website that indicated 100 - 125 lbs/acre foot of water. I can say that I can clear a jar of the water overnight with 3 - 5 crystals of alum. realize that's not worth diddly though since you don't know the weight of the crystals or the volume of water.

we added another 50 lbs about an hour ago. Guess we are now in the 'wait and see' phase. pH still looks to be in the ok range. it's about 0.7-0.8 lower than when we started.

I think we used 300# alum, 150# Hydrated lime per acre foot of water.

Moving forward 1 55# bag of SeekLeak part one will treat a half acre pond 2-3x throughout the season to reduce turbidity. I apply it in my circulator current and it’s distributed throughout my 2 acre pond. Grass carp and crayfish tend to increase turbidity starting in late May and sometimes it gets down to 12” on secchi. 24 hours following a linear polymer treatment it improves to 28-36”. Application from my dock takes 20 min and I repeat every 6-8 weeks throughout the season when Grass carp and crayfish are active. I think accumulated linear polymer is helping serve as a tackifier in pond basin locking silt and organic material in place as turbidity seems to be slowly decreasing over the past couple seasons - I think that’s a reasonable hypothesis, anyhow. If anyone wants to discuss feel free to reach out anytime - I’d like to see how other ponds respond with different ph, alkalinity, etc so we can build some turbidity mitigation science together.

Tj@hudlandmgmt.com

so I backed up and decided to use a little science (like I should've done in the first place). concentrations of alum are really small and I don't have anything that has good weight sensitivity in tenths of ounces (what I'd need unless I had a really big pond sample). so did it by making a solution and adding teaspoons at a time of the solution to a gallon of pond water. without going into the calcs, one more 50lb bag doesn't do anything but 2 more and everything drops out in a couple hours. Past that no change.

tells me two things (that I expect you all already know)
1) there is a magic concentration. Until you hit it, nothing much happens
2) you can build the concentration up (ie don't have to add all the alum at once)

so ordered more alum. fingers crossed