DIY Liquid Fert Stocks - The Planted Tank Forum
Old 09-24-2010, 03:09 AM Thread Starter
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DIY Liquid Fert Stocks

I received my set of bottles to make my own liquid stocks from dry ferts, and to make it easier for me to keep up with dosing. I'm having a little trouble with my math tonight, so I'm looking for some help. Here's what I have so far.

16 oz bottle. Approx 470 ml.
Each pump out of the bottle is .8 ml. I get approximately 590 pumps out of each bottle.
What I am thinking for convenience is 10 pumps per bottle, 3 times a week. That comes out to 8 ml per bottle.

According to EI dosing, each week I should have:
2 1/4 tsp KNO3
9/16 tsp KH2PO4
9/16 tsp CSM+B

For KNO3, it's 3/4 tsp for each dose. So 3/4 tsp per 8ml of water.
470ml / 8ml = approx 60 doses. That's 60 (3/4 tsp) doses.

Does that mean I would put 45 tsp of KNO3 in a bottle of 470 ml?

If I am off, which I think I am, please shed some light on the subject. My brain hurts tonight trying to figure this out!
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Old 09-24-2010, 04:42 AM
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Anthony

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Old 09-24-2010, 04:53 AM Thread Starter
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Well thank you. So my next dilemma, which I hadn't thought of til now. I need to remove some of the water/ferts to account for the fact that dissolving the ferts into the water will cause them to take up more space than the bottle has. So how much water do I remove?
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Old 09-27-2010, 05:21 AM Thread Starter
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Well, I did a small test run. I wasn't sure on the dissolvability (is that a word?) of each fert, so I'm going to have to get some beakers so I can figure out how much water I need per dose of each. I will be back with updates later this week.
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Old 09-27-2010, 05:58 AM
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Quote:
Originally Posted by slapnutz View Post
Well thank you. So my next dilemma, which I hadn't thought of til now. I need to remove some of the water/ferts to account for the fact that dissolving the ferts into the water will cause them to take up more space than the bottle has. So how much water do I remove?
To get around this, dissolve all the chemicals that you need to into some volume of water (say) 300 mL. Then, top off to your desired volume (in your case, 470 mL).

Quote:
Originally Posted by slapnutz View Post
Well, I did a small test run. I wasn't sure on the dissolvability (is that a word?) of each fert, so I'm going to have to get some beakers so I can figure out how much water I need per dose of each. I will be back with updates later this week.
Solubility is the word you are looking for.

The easiest way to find this information is to find the MSDS for each chemical.

Anthony

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Old 09-27-2010, 07:39 PM
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with EI dosing, you don't have to be so exact. you're overdosing the ferts anyways, and a tiny bit more or less doesn't matter.

One thing to be wary of, when you mix CSM+B, it grows this weird white fungus-like stuff in the bottle, so I've only had success mixing about a 2 week supply. Some people have success with adding excel into the mix and using DI water, but I'm not too sure how well it works out.
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Old 09-28-2010, 01:21 AM
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Did you buy pump bottles ? After reading your thread it occurred to me that the 16 ounce stress coat bottles measure 1ml per pump. Slapnutz you are officially my favorite person today! The work you did will make dosing so quick and easy I might actually do it consistently! You even did all the math so I know exactly how much to add.
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Old 09-28-2010, 01:45 AM
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You can disolve about 36g of Kno3 in 100 ml of water(use distilled) at room temp. Somewhere here is the weight of a tsp of kno3.
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Old 09-28-2010, 01:46 AM
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What you need to expect is much less amount of doses per bottle.

Potassium has a very low solubility.
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Old 09-28-2010, 01:46 AM Thread Starter
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That much KNO3 doesn't dissolve into a 16 oz bottle. I have to go back and figure out how much water it takes to completely dissolve a 3/4 tsp, then I can redo my math.

Edit: Ninja'd ever so slightly by over_stocked. I really had no idea where to start, didn't think about looking for the MSDS sheets on these. Sometime over Wed/Thurs/Fri I will have more time to work on this.

Quote:
Originally Posted by angelsword View Post
Did you buy pump bottles ? After reading your thread it occurred to me that the 16 ounce stress coat bottles measure 1ml per pump. Slapnutz you are officially my favorite person today!
Well thanks for that, but don't give me too much credit yet. When I have numbers that work, I will be happy. And yes, I purchased bottles from specialtybottle.com, that came with pumps.
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Old 09-28-2010, 02:37 AM
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Could you just half the kno3 and then double the pumps going into the tank? Either way its better than measuring powder with spoons every day.
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Old 09-28-2010, 02:44 AM
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I think it will be even more than halving it.
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Old 09-28-2010, 04:14 AM
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Quote:
Originally Posted by angelsword View Post
Could you just half the kno3 and then double the pumps going into the tank? Either way its better than measuring powder with spoons every day.
Yes, you can half the KNO3 and then double the volume. This means you are still dosing the same molar amount.

As I mentioned previously, you can look at the MSDS for solubility information, and density information should also be easily obtainable. With the density, you can convert from a volume (i.e. teaspoons) to a mass (i.e. grams), and then from there, figure out whether or not the amount you are trying to put into your container will dissolve or not.

Anthony

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