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If Alum is dissolved in water will it stay suspended? Or even if dissolved in water will it quickly sink to the bottom?

I’m wondering if I have to spread an alum slurry over the whole surface area of the pond because it sinks right away, or if I can slowly add an alum slurry to flowing water, where it will eventually mix into the whole water column.

What do you think?

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All or none. It works by the attraction of negatively charged ions... It flocks and sinks the compound you are after when the correct amount is applied. It falls through the water column slowly, attracting particulates and/or Phos on the way down.
For example. if you mix a slurry of 100lbs per acre ft of water and nothing happens in 48 hrs, you can't go back and "add" to it, you have to start over with a new, higher amount such as 200lbs per ac ft.
You have to make a slurry in a pump tank so the Alum is dissolved before blowing it out over pond surface.

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Thanks Snipe, that’s helpful. I never quite understood this about Alum. In your example, wouldn’t a half dose of Alum pull out half the suspended clay particles, making the water not fully clear but twice as clear?

Also if you know of anything helpful I could read that would be greatly appreciated.

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Ted,

I am going to go back down one level from Snipe's excellent advice.

As regards your first question about alum being dissolved or staying suspended:

Imagine putting normal table salt in a glass of water. At first you will see the salt grains settle on the bottom. If you stir it vigorously, the salt will swirl up into the water, and after you quit stirring, a little bit less will be showing on the bottom. Eventually, if you stir it up enough, ALL of the salt will be dissolved and "suspended" throughout the entirety of the water volume in the glass. (We don't actually use the term "suspended" for dissolved materials, that term only applies to discrete particles that remain in a liquid. Also, it is possible to add more salt than your volume of water is capable of dissolving.)

Since you don't want your alum "settling at the bottom of the glass", that is the reason you use a slurry of alum and dump it in the pond slowly and try to spread it rapidly with your propeller wash, etc. If you just dumped in a 100# of alum as golf-ball size chunks, it would sink to the bottom and only very slowly dissolve into your pond water. (And the chunks that sank into the bottom sediment might never dissolve.)

Your next question about things sinking right away refers to the tiny clay particles when they flocculate. (That is just a $2 word that means clump together.)

Have you ever pushed two bar magnets together trying to touch the + end of one to the + end of the other? You can actually feel the magnets repel each other. That is exactly what is happening to the tiny clay particles suspended in your pond water. They have a tiny charge and are repelling each of the other particles.

Once you get the alum dissolved in the pond, a positively charge Aluminum ion will bind to a negatively charged clay particle. It then becomes a neutral particle. These particles are now a little bit sticky. As they swirl around in the water, these particles bump into similar particles and stick together (flocculate). As the clumps grow larger, they sink to the bottom of your pond much more easily.

As for your final question about a half treatment being able to clear half of the suspended clay. Experience shows us that it just doesn't work that way.

Imagine the mice chewed 12" of insulation off of a wire in your truck. It is now touching the frame and causing a dead short. If you wrap tape on 6" of wire, it does not solve the problem, your wire is still going to short.

Even if you knock the negative charge off of half of the clay particles in your pond, they will still stay suspended. They need to clump together with the other particles to drop out of the water column.

I hope that helps understand the "reasons" a little bit more. If not, then Snipe is an actual pond expert. If you just follow his advice, that is usually the best way to get your problem solved!

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Thank you for the detailed response FishinRod, it is helpful to understand the mechanics.

If you’ll allow me I’d like to gently press on your point that “Experience shows us that it just doesn't work that way.”

I’m not sure I understand why not. If there are say 100 pounds of suspended clay particles floating around in the water (just picking a number), and half of them flocullate with the alum and sink to the bottom, won’t that mean there are only 50 pounds left of suspended clay in the water column? Once that remaining 50 lbs is evenly distributed, won’t the water clarity double, given that now there is only half as much suspended clay in the water?

What do you think FishinRod? Your thoughts Snipe would be appreciated as well, as would any thoughts from others.

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First, I've used this method many times in quite a few ponds now.
It's not linear as for the amount of Alum used vs what it sinks. Either you have enough for the particles to bind with or you don't.
Think of it like a course spider web, or 1" casting net. As it falls through the water, most particulate just goes through the net whereas a smaller mesh it builds on making the holes smaller gathering more as it goes down. It has to flocculate to work.
Alum is a positive charge by +1 because Alum is +3, sulfur -oxygen is -2, but sulfur and oxygen are non metallic so the positive charge is transferred to those elements.
Clay is a negative charge. and is attracted to the alum. Not enough Alum and the clay particles crash into each other with insufficient force to make contact and "stick".
In most cases, Type S Hydrated lime should be used as a pH buffering agent at half-rate of Alum. Great part is this adds to the positive charge and attracts even more clay in suspension to sink.
The ions only have so much power to attract and depending on the source of suspended clay, you'll be doing it twice if you don't use enough the first time.

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I find this thread interesting. I would appreciate input regarding 2 things. 1) if a pond needed 300 lbs of alum to clear and you applied 100 lbs a month for 3 months, would it clear after the 3rd application? 2) Since Gypsum is 10X cheaper than alum, does a small treatment act like alum, or will partial results be achieved?

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I like your net analogy Snipe. That’s a helpful mental model. So to come back to my original question, perhaps Alum dissolves, but really it sinks. So when you’re creating an alum slurry what you’re effectively trying to do is spread out a “liquid net” that will fall through the water column to the bottom pretty quickly, but hopefully “catch” (ie flocculate) and pull down the clay with it as it falls. You need a high enough concentration of alum so that the “net” catches all the clay as it descends through the water column. If you don’t use enough your “net” will miss a bunch of clay particles, and so you’ll simply have to throw in a “second net” with “smaller holes” (ie a higher dosage) to try again. Is that correct?

If so any thoughts on dosing? I plan to do a jar test and see what minimum it takes to clear the water, and then perhaps do 50% more than that. Does that make sense?

I also only have minnows at this point so wondering if I can get away without buffering with ag lime. My thought was to test the ph in my jar test and see what the resulting ph is and decide from there.

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Originally Posted by Eastland
I find this thread interesting. I would appreciate input regarding 2 things. 1) if a pond needed 300 lbs of alum to clear and you applied 100 lbs a month for 3 months, would it clear after the 3rd application? 2) Since Gypsum is 10X cheaper than alum, does a small treatment act like alum, or will partial results be achieved?
.
If a pond needs 300lbs of Alum to clear then 300lbs needs to be applied at one time.
Gypsum has about 5-10% of the ability to flocculate and sink particulates. It is more commonly used to raise Alkalinity.

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Originally Posted by ted_1209
I like your net analogy Snipe. That’s a helpful mental model. So to come back to my original question, perhaps Alum dissolves, but really it sinks. So when you’re creating an alum slurry what you’re effectively trying to do is spread out a “liquid net” that will fall through the water column to the bottom pretty quickly, but hopefully “catch” (ie flocculate) and pull down the clay with it as it falls. You need a high enough concentration of alum so that the “net” catches all the clay as it descends through the water column. If you don’t use enough your “net” will miss a bunch of clay particles, and so you’ll simply have to throw in a “second net” with “smaller holes” (ie a higher dosage) to try again. Is that correct?

If so any thoughts on dosing? I plan to do a jar test and see what minimum it takes to clear the water, and then perhaps do 50% more than that. Does that make sense?

I also only have minnows at this point so wondering if I can get away without buffering with ag lime. My thought was to test the ph in my jar test and see what the resulting ph is and decide from there.
Probably going to be about 200-250lbs per acre ft. and I would still use type S hydrated lime because it adds more sinking power to the particulates-besides just being a buffer-and it's cheap.
Remember, it's not Ag lime, it's hydrated (type S) lime. If pH is above 7.8 you may not need it as a buffer but it's a big part of pulling suspended particulates down.

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Originally Posted by Snipe
Originally Posted by Eastland
I find this thread interesting. I would appreciate input regarding 2 things. 1) if a pond needed 300 lbs of alum to clear and you applied 100 lbs a month for 3 months, would it clear after the 3rd application? 2) Since Gypsum is 10X cheaper than alum, does a small treatment act like alum, or will partial results be achieved?
.
If a pond needs 300lbs of Alum to clear then 300lbs needs to be applied at one time.
Gypsum has about 5-10% of the ability to flocculate and sink particulates. It is more commonly used to raise Alkalinity.
Originally Posted by Snipe
Originally Posted by Eastland
I find this thread interesting. I would appreciate input regarding 2 things. 1) if a pond needed 300 lbs of alum to clear and you applied 100 lbs a month for 3 months, would it clear after the 3rd application? 2) Since Gypsum is 10X cheaper than alum, does a small treatment act like alum, or will partial results be achieved?
.
If a pond needs 300lbs of Alum to clear then 300lbs needs to be applied at one time.
Gypsum has about 5-10% of the ability to flocculate and sink particulates. It is more commonly used to raise Alkalinity.

Snipe, we seem to have different viewpoints. I find gypsum much more effective than 5-10% of alum. Todd Overton turned me on to gypsum as an alternative to alum, at $160 per ton, the results are a no brainer. Even small applications are noticeable, maybe it's the difference in water chemistry between locations.

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Need to read up on that, I think Todd is giving you the "safest" way to clear it.
Even American Sport Fish hatchery and Texas A&M support Alum as the absolute best method-BUT..you gotta be careful in how you apply it and use the right amount of Hydrated lime.
Chemistry could be different, and I will not argue with Todd's recommendations.

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I had edited this post to read my findings on the amounts of both products and it kicked me off.. Doesn't matter, use what works and is readily available to you.

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Todd tends to go with the safest route when dealing with DIY pond owners. I spread gypsum after every drain and refill on my hatchery pond, it raises the hardness, and clears up the water in a day or two. I had great results spreading gypsum in George Glazener's pond 5-6 years ago. IIRC we added 30 tons, shut off the aeration, and the water cleared up in 3 days.

Highfyler and I treated one of my cow tanks with alum and hydrated lime as a test run, and it cleared up pdq. What surprised me was that even with the cows stomping around in it, the water stayed fairly clear for a few months.


AL

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Be sure of your gypsum source. Some tried foreign made wall board only to find out the gypsum source was bad.

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I have two five gallon buckets of alum that I bought to clean a turbid new pond. I decided not to use. Would be glad to sell if someone is interested please PM me. Probably too expensive to ship but could meet up maybe.

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Kind of off topic here, but I had our pond treated when it was built. Rex (Rainman) came out with his pontoon boat and sprayed the alum mixture. The transformation was incredible. The water went from clay colored brown to crystal clear in a very short time.
I’m not sure that the clay wouldn’t have settled out anyway, but the water never would have cleared up to that degree.
So now, ten years later, did it make any difference? A few weeks ago we had 20” clarity measured with the Seiichi disk. I realize that’s all algae dependent, but did the alum treatment make any difference? Would I have been better off investing in aeration? I really have no idea. The water was pretty amazing, at least for a few weeks.
However, even today if I wade out off the bank, clouds of clay particles come up around my footsteps, but immediately settle back to the bottom. Is this natural, or the residual effects of the alum?
Just food for thought here. I’m obviously not a scientist.


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Originally Posted by Eastland
Originally Posted by Snipe
Originally Posted by Eastland
I find this thread interesting. I would appreciate input regarding 2 things. 1) if a pond needed 300 lbs of alum to clear and you applied 100 lbs a month for 3 months, would it clear after the 3rd application? 2) Since Gypsum is 10X cheaper than alum, does a small treatment act like alum, or will partial results be achieved?
.
If a pond needs 300lbs of Alum to clear then 300lbs needs to be applied at one time.
Gypsum has about 5-10% of the ability to flocculate and sink particulates. It is more commonly used to raise Alkalinity.
Originally Posted by Snipe
Originally Posted by Eastland
I find this thread interesting. I would appreciate input regarding 2 things. 1) if a pond needed 300 lbs of alum to clear and you applied 100 lbs a month for 3 months, would it clear after the 3rd application? 2) Since Gypsum is 10X cheaper than alum, does a small treatment act like alum, or will partial results be achieved?
.
If a pond needs 300lbs of Alum to clear then 300lbs needs to be applied at one time.
Gypsum has about 5-10% of the ability to flocculate and sink particulates. It is more commonly used to raise Alkalinity.

Snipe, we seem to have different viewpoints. I find gypsum much more effective than 5-10% of alum. Todd Overton turned me on to gypsum as an alternative to alum, at $160 per ton, the results are a no brainer. Even small applications are noticeable, maybe it's the difference in water chemistry between locations.




I think several studies show Gypsum only works about 50% of the time and Alum will work 100% when both are properly applied. Cost can vary widely for both Gypsum and Alum, so I disagree with Alum being 10 times the cost, because application is different and can cost considerably more for gypsum...Every time I priced gypsum, Alum was considerably less expensive because it is not used in most areas. If forced to buy gypsum in smaller 40# bags the cost for gypsum per ton is $800...to keep comparisons fair, Alum is priced at $0.40-$0.60 per pound ($800-$1200 per ton). Overton has Gypsum listed as $195/ton currently...At 500-800 pounds of gypsum, or 250-300 pounds of alum per acre foot recommended "doses", final costs will vary, but unlikely that alum is 10X more.. To answer your question on alum "dosage"...If a pond needs 300 pounds of alum to be cleared, no, adding 100 pounds a month (or week) will not work, but if you add 150-200 pounds one day and it does not clear, you could add,100-150more pounds the very next day and it will likely clear...Alum does not dissolve in water, and slowly sinks...I have never used Gypsum, because when I am paid to clear a pond, using something that only has a 50% chance of working vs knowing I will accomplish what I am being paid for, Alum is truly a no brainer for me...and not much more expensive since it is easier to handle and apply...It all comes down to knowing what you want, knowing the chemicals, weighing the risks of success vs failure and true costs for the area and experience level, and making a personal choice on which to use

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Hey Rainman!!

I know nothing about gypsum, alum and pounds per acre foot, but I want to say THANK YOU for coming back to the forum and sharing again. We really value your time and experience and many have ongoing questions about turbid water, how to clear it, how to do it safely, how long it lasts etc.

You can see just above your post that SetterGuy had some questions for you about how long your work at his pond should be expected to last.

Please check in once in a while! It is appreciated!

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Todd Overton's fish farm in TX sells a ton of gypsum for $160 or .08 cents per lb. Alum is $50 per 50 lb. bag, $1 per lb. So, alum is actually 12.5 times more expensive here. I have used both and for my water chemistry, gypsum has a lot more bang for the buck. It also eliminates any PH/fish kill issues. You can also notice subtle differences in water clarity when spreading smaller applications. A simple jar test using both alum and gypsum would be a good starting point to see what works. There is no dispute that Alum works almost immediately and is most effective.

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Originally Posted by Eastland
Todd Overton's fish farm in TX sells a ton of gypsum for $160 or .08 cents per lb. Alum is $50 per 50 lb. bag, $1 per lb. So, alum is actually 12.5 times more expensive here. I have used both and for my water chemistry, gypsum has a lot more bang for the buck. It also eliminates any PH/fish kill issues. You can also notice subtle differences in water clarity when spreading smaller applications. A simple jar test using both alum and gypsum would be a good starting point to see what works. There is no dispute that Alum works almost immediately and is most effective.

Eastland, what does the alum cost per ton there? Buying a ton of gypsum is a lot different than buying a bag of alum. Gypsum here in a 50# bag costs $59.47.


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Originally Posted by esshup
Originally Posted by Eastland
Todd Overton's fish farm in TX sells a ton of gypsum for $160 or .08 cents per lb. Alum is $50 per 50 lb. bag, $1 per lb. So, alum is actually 12.5 times more expensive here. I have used both and for my water chemistry, gypsum has a lot more bang for the buck. It also eliminates any PH/fish kill issues. You can also notice subtle differences in water clarity when spreading smaller applications. A simple jar test using both alum and gypsum would be a good starting point to see what works. There is no dispute that Alum works almost immediately and is most effective.

Eastland, what does the alum cost per ton there? Buying a ton of gypsum is a lot different than buying a bag of alum. Gypsum here in a 50# bag costs $59.47.

He doesn't sell it by the ton, but if anyone knows where alum is sold by the ton, I would like to know what the price is. I've struck out trying to find someone who sells it by the bucket load.

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Just for reference, Smith Creek Fish Farm sells Alum by the ton for $1398.99. Using that number Alum is 8.74 times more expensive to apply than gypsum in my area. My results show gypsum to be 2/3rds as effective as alum, making it a no brainer in my situation. Just trying to save some people some money while avoiding the PH issue regarding fish kills. Which I believe Lusk's crew ran into in the beginning when he had to replace a customer's fish...an old story told during a Pond Boss convention back 20 years ago.

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Level7chemical.com sells 1 ton of alum for $1224.00 and they offer a 10% off coupon on orders over $750. I bought from them last year and had no problems. It was a LOT of work to spread the alum. I don't think I'd do it again. Gypsum had no effect on my pond. I think the lesson i learned was just to relax and let nature do its thing.

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Gypsum being effective "50% of the time" "I think" is a super scientific way to describe it. If you're testing hardness and completing turbidity testing before applying it, you know exactly how much you need and whether or not it will be effective.
Also calculate the amount of hydrated lime you will need during application into your cost when using alum (unless you want to pH kill of the BOW), as well as the PPE that I would highly recommend unless you want to be inhaling them both the whole time.

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