Auto Dosing And Stirring

ianmills122 · Sep 22, 2018

For anyone that is using an auto doser, do you employ some sort of auto stirring mechanism to keep the ferts suspended?

I have been auto dosing ferts for a few years now using a Neptune DOS. It occurred to me that when I first mix up the ferts for my dosing containers i get lack luster plant growth and then towards the end of the dosing container i start getting better plant growth. There is a lot of settling that occurs and sits on the bottom of the dosing containers. My thought is if i employ a magnetic mixer or some kind of micro pump in the dosing container that stirs the mix every day before it gets pumped into the water column i might get more consistent growth.

For reference I employ the PPS Pro method and have 2 separate dosing containers. One with Micros and one with Macros.

Does anyone have any experience with employing some sort of stirrer?

echocinco · Sep 23, 2018

The magnetic mixer sounds like a great idea, but I feel like it would use a lot of electricity unless you set it up to a timer and synchronize it so that it stirs when the autodoser is ready to dose.

Also, do you know how much a magnetic stirrer would cost? I'm interested in this idea also!

ashtonfitzgerald · Sep 23, 2018

I DIY'd a magnetic stirrer for testing water and total build cost was less than $10. The magnetic stir bars from Amazon cost as much as the stirring apparatus. It's a 12dc computer fan with a hard drive magnet mounted to it. I usually power it at 5 volts using a USB wall-wart and that gives a nice gentle stir for testing water parameters. At 12v with a large stirbar it will create a vortex in a 1qt mason jar no problem.

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Allwissend · Sep 23, 2018

ianmills122 said:
It occurred to me that when I first mix up the ferts for my dosing containers i get lack luster plant growth and then towards the end of the dosing container i start getting better plant growth. There is a lot of settling that occurs and sits on the bottom of the dosing containers. My thought is if i employ a magnetic mixer or some kind of micro pump in the dosing container that stirs the mix every day before it gets pumped into the water column i might get more consistent growth.

Hi ianmills,

stirring the fertilizer solutions can be done as mentioned above, either get a magnetic stirrer or go DIY and create your own. And nothing wrong with mixing.

However the macro and micro solutions should not have any precipitate /settling. After complete dissolution of the salts they should stay like that. Do you notice the precipitate right after you make the solutions or they cool down ? If yes, the solutions are either too concentrated - mixing might help. If the precipitates are seen later they are likely from microbiological contamination - mixing won't help.

echocinco · Sep 23, 2018

Allwissend said:
Hi ianmills,

stirring the fertilizer solutions can be done as mentioned above, either get a magnetic stirrer or go DIY and create your own. And nothing wrong with mixing.

However the macro and micro solutions should not have any precipitate /settling. After complete dissolution of the salts they should stay like that. Do you notice the precipitate right after you make the solutions or they cool down ? If yes, the solutions are either too concentrated - mixing might help. If the precipitates are seen later they are likely from microbiological contamination - mixing won't help.

Whoops! Alliwissend is totally right about solutions normally not having precipitate. I got too excited about making/adding cool new stuff to my aquarium that I overlooked that part =D.

FME, precipitate in a macro solution is usually from microbio contamination whereas precipitate in a micro solution (usually my K or Mg solution) is from superconcentration depending on where the crystals are located. Precipitate crystals inside the solution bottle are usually due to oversaturation. Precipitate on the outside of the bottle is just normal crystallization due to evaporation. Precipitate inside the tubing is a mix of both oversaturation and evaporation.

Given this, I'd guess what's happening in your situation is that you're not dosing enough, so that when you get to the bottom of the bottles you are dosing extra w/ the crystals and the plants are responding to the extra nutrients.

I'd also make an additional guess that the macros are the culprit and that there is at least one specific macro nutrient that you need to dose more of (e.g. N or K). I dose K and N separately because I like to overdose on K to keep my green plants extra green. I also dose MgSO4 separately with the K per Dennis Wong's recommendations on his website.

EDIT: I misused the term supersaturation which refers to when you are able to dissolve more than the max solubility of a solute in a solution (albeit temporarily). Saturation refers to when you've reached the max solubility of a solution which is what happens when try to dissolve too much solute and you're left with undissolved crystals at the bottom of the container.

ianmills122 · Sep 23, 2018

Allwissend said:
Hi ianmills,

stirring the fertilizer solutions can be done as mentioned above, either get a magnetic stirrer or go DIY and create your own. And nothing wrong with mixing.

However the macro and micro solutions should not have any precipitate /settling. After complete dissolution of the salts they should stay like that. Do you notice the precipitate right after you make the solutions or they cool down ? If yes, the solutions are either too concentrated - mixing might help. If the precipitates are seen later they are likely from microbiological contamination - mixing won't help.

When I make the macro and micro mixes I use dry ferts and put them into 500ml plastic bottles, then add cool RO water. I refrigerate the mix overnight, then poor them into my dosing containers for the doser to suck up. Should I be using hot RO water? Typically I shake the crap out of the bottles but there is always some sort of sediment free floating from the get go. I also put Flourish Excel into the dosing containers to help with mold etc.

ianmills122 · Sep 23, 2018

ashtonfitzgerald said:
I DIY'd a magnetic stirrer for testing water and total build cost was less than $10. The magnetic stir bars from Amazon cost as much as the stirring apparatus. It's a 12dc computer fan with a hard drive magnet mounted to it. I usually power it at 5 volts using a USB wall-wart and that gives a nice gentle stir for testing water parameters. At 12v with a large stirbar it will create a vortex in a 1qt mason jar no problem.

Sent from my iPhone using Tapatalk

This is a great idea! Thanks.

ianmills122 · Sep 23, 2018

echocinco said:
The magnetic mixer sounds like a great idea, but I feel like it would use a lot of electricity unless you set it up to a timer and synchronize it so that it stirs when the autodoser is ready to dose.

Also, do you know how much a magnetic stirrer would cost? I'm interested in this idea also!

All the ones I have looked at are between $36 all the way up into the couple hundreds. Seems kind of pricey for such a simple device.

ianmills122 · Sep 23, 2018

When mixing dry ferts with RO water, do you guys mix it together hot or cold? Maybe I have been mixing my solutions wrong all this time and i don't even need a mixer?

echocinco · Sep 23, 2018

When I mix dry ferts, I mix them in cold water but make sure I measure the amount of solute and water precisely enough to make sure I don't supersaturate my solutions. Different solutes have different solubilities at different temperatures. Some solutes increase in solubility with higher temperature others will decrease in solubility with higher temperatures. Generally speaking, I want to say that most of the macronutrients solutes we work with have greater solubility at higher temperatures.

With this mind, when you dissolve your micros in hot water, you're able to dissolve more in the solution than you would if it were at a lower temperature (e.g. room temperature). Since you are cooling your solutions after dissolving, you might actually be oversaturating your solution which is why you get precipitate when you prep the solutions into your doser.

If you are measuring out each of your macros separately, you can reference solubility tables to see how much of each you can dissolve at a given temperature. You can find the tables for each of the compounds Wikipedia and use the water solubility at 20deg C as your baseline unless you store your solutions in the refrigerator (then you should probably use the solubility at 0deg C as your reference).

ianmills122 · Sep 23, 2018

echocinco said:
When I mix dry ferts, I mix them in cold water but make sure I measure the amount of solute and water precisely enough to make sure I don't supersaturate my solutions. Different solutes have different solubilities at different temperatures. Some solutes increase in solubility with higher temperature others will decrease in solubility with higher temperatures. Generally speaking, I want to say that most of the macronutrients solutes we work with have greater solubility at higher temperatures.

With this mind, when you dissolve your micros in hot water, you're able to dissolve more in the solution than you would if it were at a lower temperature (e.g. room temperature). Since you are cooling your solutions after dissolving, you might actually be oversaturating your solution which is why you get precipitate when you prep the solutions into your doser.

If you are measuring out each of your macros separately, you can reference solubility tables to see how much of each you can dissolve at a given temperature. You can find the tables for each of the compounds Wikipedia and use the water solubility at 20deg C as your baseline unless you store your solutions in the refrigerator (then you should probably use the solubility at 0deg C as your reference).

So when i measure my ferts out I use a scale and measure it out precisely. However when i add water i just fill the container with ro water up to the 500 ml water level. I am confused what i might do differently by knowing the solutability of each ingredient?

echocinco · Sep 23, 2018

If you're measuring out 500 mL worth of solute, then you need to add 500 mL of water (not just fill it up to the 500 mL mark since that will actually be less than 500 mL unless you are completely dissolving everything and then topping it off to 500mL). Either way probably wont make much a difference unless you are really maxing out your concentration. If you go for 80% saturation, it shouldnt really matter what order you add the solute and water since I doubt your container is 20% full with dry fertz before you start pouring water in.

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Allwissend · Sep 24, 2018

echocinco said:
If you're measuring out 500 mL worth of solute, then you need to add 500 mL of water (not just fill it up to the 500 mL mark since that will actually be less than 500 mL unless you are completely dissolving everything and then topping it off to 500mL)

To put it in other words the total volume of the solution (salt+water) should be 500mL.

You can use either hot or cold water as long as it fully dissolves and stays fully dissolved at room temperature. In general using warmer water makes the process faster.

Try this:
1. Use 1/4 the mass of salts in the same bottle volume
2. Adjust pumps to dose 4*the current volume

And see if you observe less precipitation. This will give you the same concentration in the aquarium while using a more dilute solution.

ianmills122 · Sep 24, 2018

Allwissend said:
To put it in other words the total volume of the solution (salt+water) should be 500mL.

You can use either hot or cold water as long as it fully dissolves and stays fully dissolved at room temperature. In general using warmer water makes the process faster.

Try this:
1. Use 1/4 the mass of salts in the same bottle volume
2. Adjust pumps to dose 4*the current volume

And see if you observe less precipitation. This will give you the same concentration in the aquarium while using a more dilute solution.

Will do. Thanks for the advice.

Auto Dosing And Stirring

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