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Discussion Starter · #1 ·
What’s your protocol with using RO water in your tank?

What do you add to it beforehand and how much do you add per day 25L/ 5.5g

How do you test it and what for etc?


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I personally add this to my RO water for use in a high tech, Aquasoil tank:

12.5ppm NO3 using KNO3 (fertilizer) - My soil has stopped leaching ammonia so I will need to tart adding more NO3 in the near future.
10ppm PO4 using KH2PO4 (fertilizer) - My soil is uptake PO4 at a high rate, once it stops I will lower this dose slightly.
25ppm K using KNO3 / KH2PO4 / K2SO4 (fertilizer)

25ppm Ca using CaSO4 (GH remineralizer)
12.5ppm Mg using MgSO4 (GH remineralizer)

I add these, and fully dissolve them into my new water in a storage tote. I heat the water to match the tank temp and perform 1 x weekly 68% water change.
 

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I add the RO water during my water change (re-mineralized) and when topping off (pure RO water) due to evaporation.

Generally, it is best to re-mineralize your RO water to a TDS level that is within 10% of your tank TDS level. Doing so reduces the possibility of osmotic disruptions to your fauna. So, at a minimum, try to match the GH and KH of your tank by adding the Ca, Mg and bicarbonate salts to the container holding your RO water, before adding it to your tank. This means that you will need a TDS meter, a GH test kit and KH test kit, all of which are inexpensive.

There are re-mineralizing mixes, such as Seachem’s Equilibrium, that will do all of this. However, many of us prefer adding the salts separately in order to better control these levels. If you wish to do that, you will add Ca (via CaCl, CaSO4, etc.) and Mg (via MgSO4, MgCl, etc.) for the GH components and KHCO3 or K2CO3 for the bicarbonate (KH) component. You can use the RotalaButterfly calculator for any of these, plus your fertilizers to determine dosing levels.

The above parameters are only the water hardness and alkalinity aspects. In a planted tank, you also should strive for consistent fertilizer levels. A water change involving RO water will reduce your fertilizer levels, as well as the hardness and alkalinity aspects, by the percentage of the water change. So, you should add those fertilizers back at a level that you wish to maintain in your tank (usually by the percentage of the w/c). However, these other fertilizers can be added after your water change.

Having said all of this, you should decide what GH and KH levels that you want your tank to have on a steady basis. Then, use the above procedure to maintain those levels. One of the benefits of using RO water is that you can now customize this to your liking. The same goes for your other fertilizers.
 

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I have a 10g low tech (no CO2). I drain 60-70% of the tank water, then refill with RO water. After that I dose the tank with an all-in-one fertilizer I got from a local hobbyist. It's a dry mix that I have dissolved in RO water, so I guess it's a liquid fertilizer. Works for me. I also top off with pure RO water to account for evaporation.
 

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Discussion Starter · #5 ·
I add the RO water during my water change (re-mineralized) and when topping off (pure RO water) due to evaporation.

Generally, it is best to re-mineralize your RO water to a TDS level that is within 10% of your tank TDS level. Doing so reduces the possibility of osmotic disruptions to your fauna. So, at a minimum, try to match the GH and KH of your tank by adding the Ca, Mg and bicarbonate salts to the container holding your RO water, before adding it to your tank. This means that you will need a TDS meter, a GH test kit and KH test kit, all of which are inexpensive.

There are re-mineralizing mixes, such as Seachem’s Equilibrium, that will do all of this. However, many of us prefer adding the salts separately in order to better control these levels. If you wish to do that, you will add Ca (via CaCl, CaSO4, etc.) and Mg (via MgSO4, MgCl, etc.) for the GH components and KHCO3 or K2CO3 for the bicarbonate (KH) component. You can use the RotalaButterfly calculator for any of these, plus your fertilizers to determine dosing levels.

The above parameters are only the water hardness and alkalinity aspects. In a planted tank, you also should strive for consistent fertilizer levels. A water change involving RO water will reduce your fertilizer levels, as well as the hardness and alkalinity aspects, by the percentage of the water change. So, you should add those fertilizers back at a level that you wish to maintain in your tank (usually by the percentage of the w/c). However, these other fertilizers can be added after your water change.

Having said all of this, you should decide what GH and KH levels that you want your tank to have on a steady basis. Then, use the above procedure to maintain those levels. One of the benefits of using RO water is that you can now customize this to your liking. The same goes for your other fertilizers.
This is perfect info, thank you, I personally use a product similar to seachem equilibrium, I probably will go to that soon, my tank and water parameters are pretty good at the moment but to be honest I just measure it by eye, I’m looking to getting a TDS meter to measure that & also I see seachem do a digital scale spoon for a reasonable price so I may get that also, just to ensure consistency.


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The above parameters are only the water hardness and alkalinity aspects. In a planted tank, you also should strive for consistent fertilizer levels. A water change involving RO water will reduce your fertilizer levels, as well as the hardness and alkalinity aspects, by the percentage of the water change. So, you should add those fertilizers back at a level that you wish to maintain in your tank (usually by the percentage of the w/c). However, these other fertilizers can be added after your water change.
Hi,
Can you please elaborate more on this paragraph? When I do my 50% water change is at 6 PM every Saturday and add fertilizer every morning. Are you saying that after the water change I should add a daily dose even though I added one that morning and will do again the morning after.

Thanks!!
 

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Hi,
Can you please elaborate more on this paragraph? When I do my 50% water change is at 6 PM every Saturday and add fertilizer every morning. Are you saying that after the water change I should add a daily dose even though I added one that morning and will do again the morning after.

Thanks!!
I view macro dosing as a two-step process. If I do a 50% water change, I will want to immediately add macros at a level that matches my target level (micros are dosed only on a daily basis, for daily consumption). For example; if I maintain a 5ppm PO4 level, I know that a 50% water change will reduce that to 2.5ppm when the RO water is added. So, I immediately dose 2.5ppm PO4 after the water change. The second step is the maintenance dosing (I use an auto-doser). For example; if I reach the end of the week with 4ppm PO4, I know I want to add 1ppm throughout the week. If dosed daily, that would be .15ppm PO4 daily.
 

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I view macro dosing as a two-step process. If I do a 50% water change, I will want to immediately add macros at a level that matches my target level (micros are dosed only on a daily basis, for daily consumption). For example; if I maintain a 5ppm PO4 level, I know that a 50% water change will reduce that to 2.5ppm when the RO water is added. So, I immediately dose 2.5ppm PO4 after the water change. The second step is the maintenance dosing (I use an auto-doser). For example; if I reach the end of the week with 4ppm PO4, I know I want to add 1ppm throughout the week. If dosed daily, that would be .15ppm PO4 daily.
Thanks!! Your explanation makes sense, however I do not have the knowledge to do the same. I used salts in the beginning and it was a struggle not knowing what went into the tank then I changed to TROPICA fertilizers. How do you measure all this in PPM's?
 

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A TDS meter will allow you to determine if you are drifting in total parameters. See this post: TDS meter.

You might also consider the TDS technique, in more detail, by reviewing the PPS approach, here: PPS
 

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Thanks!! Your explanation makes sense, however I do not have the knowledge to do the same. I used salts in the beginning and it was a struggle not knowing what went into the tank then I changed to TROPICA fertilizers. How do you measure all this in PPM's?
First you estimate the amount of water in liters in your tank. You do this by multipliying how many gallons your tank has by 3.785 to get the liters in the tank. Then you multiply that by 0.85 to account for displacement. After that you decide what your target nutrient concentration will be. Say you want 20 ppm. You then multiply that target ppm by the estimated amount of water you have in your tank. So if you have 100 liters, your answer will be a 2,000 mg dose of whatever to get 20 ppm of whatever in your tank. But 2,000 mg of whatever would not be a big enough dose to get 20 ppm. Every fertilizing salt has a percentage of the stuff you want to get out of it. KNO3 for example has 61.31% NO3 in it. You have to divide the above 2,000 mg by this percentage to get the dose of KNO3 for your tank. 2,000 mg KNO3/61.31% = 3,262 mg KNO3 to get your target of 20 ppm NO3 in 100 liters of water. Hope this answers your question. Hope this helps.
 
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