Dissolving Potassium Sulfate in DIY mix..?? - The Planted Tank Forum
 
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post #1 of 15 (permalink) Old 11-12-2003, 05:57 AM Thread Starter
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Ok.. I got some Potassium Sulfate from Light supply and using Chuck's calculator, I came up with a mixture of 17 tablespoons to go into my 710ml aquafina bottle. I mixed this together and it wouldn't dissolve so I boiled it in a pan for about 15 minutes but it still wouldn't dissolve. After several days, I still have a 710ml bottle with 2 or 3 inches of powdery Potassium Sulfate settling at the bottom. How do I get this stuff to mix properly so I can dose it?

I also have some Potassium Nitrate and Mono Potassium Phosphate that I will need to mix.

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post #2 of 15 (permalink) Old 11-12-2003, 06:26 AM
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Don't bother; just add it dry to the tank (your fish will be fine). Use Chuck Gadd's Calculator (enter 1mL for "Amount of water to mix with") to determine how much to add.
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post #3 of 15 (permalink) Old 11-12-2003, 07:22 AM Thread Starter
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Ok so the potassium isn't trapped inside the powder? How is it released into the water column? I really don't know anything about chemistry but it doesn't seem like the plants could make very good use of the potassium- unless it dissolves in the aquarium better than my water bottle.
Is this a time release kind of thing? I guess I'll give it a shot since the fishes won't care.

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Eheim Pimp #159: Eheim 2233 Ecco & Eheim 2211 canisters.

55g planted- 80deg F.
2 Coralife Aqualights 65w 6700k + 2 15w lights .
Pressurized CO2 5lb tank.
Substrate: 1" Tex blast, 2" Flourite & Eco Complete, ~.25" sand.

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post #4 of 15 (permalink) Old 11-12-2003, 08:06 AM
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Potassium sulfate has very limited solubility in water. The amount of powder you've proposed to dissolve will not fully dissolve into your Aquafina bottle and will thus throw off your stock solution concentration, but the smaller amount of powder you'd add to the tank to achieve proper levels will easily dissolve to completion in short order.
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post #5 of 15 (permalink) Old 11-12-2003, 08:01 PM Thread Starter
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I understand now. I think what I'll do is shake the bottle up real good and take measured doses out of it while it's still mixed up. Next time I'll just dose straight into the tank.

Will Potassium Nitrate and Mono Potassium Phosphate act the same way or are they more soluable?

Thanks!

Carpet-Pond

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55g planted- 80deg F.
2 Coralife Aqualights 65w 6700k + 2 15w lights .
Pressurized CO2 5lb tank.
Substrate: 1" Tex blast, 2" Flourite & Eco Complete, ~.25" sand.

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post #6 of 15 (permalink) Old 11-12-2003, 09:39 PM
 
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Carpet,

You can go with 2La's suggestion or you may try this.....

I dont like adding powders to the tank because my fish think its food..LOL...they dont get hurt by it though!

I take the dosage off of Chucks calculator using 1ml like 2La said. I then take a tupperware bottle and fill it with tank water. Next, I put the powder in that and "shake shake shake....da da dada da....shake shake shake...." <---KC and Sunshine band tune optional. It dissolves into solution and then I add to the tank.

Works well for me and voila! Thats it!

Mike

2la's way works just as well...I just like the mixing portion I do.
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post #7 of 15 (permalink) Old 11-13-2003, 05:48 AM Thread Starter
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Quote:
"shake shake shake....da da dada da....shake shake shake...." <---KC and Sunshine band tune optional.
:lol:

LOL.... I was thinking the theme song to Sanford and Son would go well too!

Also, when I put 1ml into the amount of water to add solution to, I get nothing.. actually one time I got Infinity Potassium when I was playing with it but I don't think that's what I was looking for. :shock: I'm sure the plants would look -really- nice to the fish then!

Anyway, 17 tablespoons mixed with 710ml makes a mix of 1ml per 1.02ppm potassium dose which now that I think (really hard) about it, makes sense. I think I'll try dosing with a 5 gallon bucket next time and stir it with a gravel vac or something. 17 tbspns pretty much used up the entire bag (1lb.) of potassium so I may as well keep it stored in there til it's used up.

That reminds me.. how long does it take for this stuff to go bad? Should it be kept in the fridge?

Carpet-Pond

Eheim Pimp #159: Eheim 2233 Ecco & Eheim 2211 canisters.

55g planted- 80deg F.
2 Coralife Aqualights 65w 6700k + 2 15w lights .
Pressurized CO2 5lb tank.
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post #8 of 15 (permalink) Old 11-14-2003, 03:09 PM
 
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Originally Posted by Carpet-Pond
Anyway, 17 tablespoons mixed with 710ml makes a mix of 1ml per 1.02ppm potassium dose which now that I think (really hard) about it, makes sense.
To give you an idea of why is won't dissolve. Potassium sulfate has a maximum solubility of 12grams per 100ml. 12 grams is about 3/4 tablespoon of K2SO4. For your 710ml the maximum amount you could dissolve would be about 4 and 3/4 tablespoons of K2SO4. Your 17 tablespoons of K2SO4 would weight about 306 grams and would require about 2550ml of water for maximum solubility. And maximum solubility is difficult to achieve without using hot water. This is why almost everyone doses K2SO4 dry.
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post #9 of 15 (permalink) Old 11-14-2003, 03:55 PM
 
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Quote:
Originally Posted by 2la
Don't bother; just add it dry to the tank (your fish will be fine). Use Chuck Gadd's Calculator (enter 1mL for "Amount of water to mix with") to determine how much to add.
Ok, now THAT makes sense to me.

I've been grappling with this too.

Ok, so you're dosing dry chemicals. How do you know how much to put in over time to maintain your target range on Magnesium and all of the Potassiums? I can measure phosphates and nitrates.

Finally, is the potassium in potassium sulfate equal to the potassium in potassium chloride? The following quote from Chuck's page leads me to believe that they are interchangeable, but I just want to make sure:
Quote:
There are several commercial aquarium plant additives that contain potassium. You can also obtain Potassium Sulfate (K2SO4) or Potassium Chloride (KCl) from a gardening store as a source. K2SO4 is often referred to as "Sulfate of Potash", and KCl is referred to as Muriate of Potash. I only recently (in the past couple months) starting adding potassium, and the improvement in plant growth and health has been amazing.
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post #10 of 15 (permalink) Old 11-14-2003, 04:14 PM
 
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Finally, is the potassium in potassium sulfate equal to the potassium in potassium chloride? The following quote from Chuck's page leads me to believe that they are interchangeable, but I just want to make sure
Chucks calculator has both on the menu. They are both for dosing pottasium, but one adds sulfate to the tank and one adds chloride. They carry different ratios of pottasium so you must use the calculator to determine how much each will add.
Quote:
Don't bother; just add it dry to the tank (your fish will be fine). Use Chuck Gadd's Calculator (enter 1mL for "Amount of water to mix with") to determine how much to add.
Not all nutrients should be dosed dry.
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Ok, so you're dosing dry chemicals. How do you know how much to put in over time to maintain your target range on Magnesium and all of the Potassiums? I can measure phosphates and nitrates.
For pottasium its simple.... you can safely assume that your tap water contains zero potassium. First time dose for the entire tank volume, thereafter dose for the volume of water changed. Magnesium makes up a part of the GH number and this varies from one area to the next. They sell magnesium test kits though I doubt anyone here uses them, including myself. I normally mix the micros including mg, as per the PMDD formula and dose NPK seperately at water change time. NPK needs are pretty easy to determine with tests. Micros are a little more fuzzy. I dose and watch the plants, this can take weeks to determine dosing. For me its still an ongoing kinda trial and error thing. Use the PMDD dosing reccomendation to start and adjust from there. With high light and CO2, chances are you'll be adjusting the micro dosage upward as time goes on.

Marcel
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post #11 of 15 (permalink) Old 11-14-2003, 04:25 PM
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Quote:
Originally Posted by m.lemay
Not all nutrients should be dosed dry.
I was referring only to the potassium sulfate in question, but just out of curiosity, which nutrients should not be dosed dry?
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post #12 of 15 (permalink) Old 11-17-2003, 01:42 AM
 
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Quote:
Originally Posted by 2la
Quote:
Originally Posted by m.lemay
Not all nutrients should be dosed dry.
I was referring only to the potassium sulfate in question, but just out of curiosity, which nutrients should not be dosed dry?
I definitely would not dose plantex or KNO3 dry. Both of those are needed in very low amounts and could easily be overdosed when dry. It's better to make a stock solution in a 500ml water bottle and dose that into the tank for consistency and accuracy. I use fleet enema for phosphates which is already a liquid. I've never used potassium phosphate so I'm not sure about that one but I'd imagine that it also would be difficult to dose dry accurately. We all know what an overdose of phosphate can do to a tank. :shock:


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post #13 of 15 (permalink) Old 11-17-2003, 03:29 AM
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I dose KNO3 dry. The only caveat is you have to account for the different grain size from mixture to mixture, but once you do that there's no danger in dosing it dry at all. In fact, I had problems with KNO3 crystallizing out of solution, and I'd imagine that threw off my dosing more than my current method of dosing it dry.
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post #14 of 15 (permalink) Old 11-17-2003, 04:01 PM
 
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If it works for you, leave it alone. I have no problems with my kno3 falling out of solution.
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post #15 of 15 (permalink) Old 11-17-2003, 06:52 PM
 
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It should be noted that dosing dry is great for larger tanks, but adding KNO3 and especially KH2PO4 is really difficult to accurately do for tanks smaller than 20G. For those smaller tanks mixing a stock solution is a much better choice.
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