yet another DIY KH,GH + nutrient dose for RODI water - The Planted Tank Forum
 
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post #1 of 8 (permalink) Old 05-04-2019, 06:12 PM Thread Starter
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Lightbulb yet another DIY KH,GH + nutrient dose for RODI water

Hi all,

The last 2 months I am running a 30 g aquarium consisted of HC and some pervula mini, I use only RODI water and I have tropica aquasoil as substrate. I provide CO2 gas and strong lights using led lamps. Up to now, I used commercial salts for raising KH,GH parameters and tropica specialized for the nutrition of the plants.

Recently, I started reading about different fertilization dosing strategies and I am in the process of creating my own lean "All in one" dosing routine in order to control the necessary parameters without standard weekly water changes. (I know I am asking a lot)

After some research on forums and some tests on online calculators, I end up to those compounds below:

(All the doses are calculated for ~ 30 gals)

KHCO3: 7 grams (yields) => 28 ppm Κ + 2 dKH
MgSO4: 5 grams => 5 ppm Mg + 7 ppm S + 1.2 GH
CaSO4: 10 grams => 10 ppm Ca + 8 S + 1.5 GH
CaCl2: 5 g => 5 ppm Ca + 9 ppm CI + 0.8 GH

So, we have:
  • 2 KH
  • 3.5 GH
  • 28 ppm K
  • 15 ppm Ca
  • 5 ppm Mg
  • 9 ppm Cl

My plan for the NO3 and PO4 is to provide it from the bioload and then for the micronutrients use a commercial Trace Element mix (dry powder)

With the above, THEORETICALLY I can get all the necessary Macro and Micro nutrients that I need so I would like to ask you since you are much more experienced than me.

With the right water monitoring ( continues water testing) and plant/fish observation is this plan possible?


Thanks a million!
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post #2 of 8 (permalink) Old 05-04-2019, 06:24 PM
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Does tropica aqua soil strip KH from the water?
ADA does, that is why I ask.


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post #3 of 8 (permalink) Old 05-05-2019, 02:32 PM Thread Starter
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Unfortunately, I couldnt find any official information for this aquasoil, I know that the first 4+ weeks the substrate leaches out ammonia like ADA but in smaller portions. I was performing 2 50% water changes the first 5 weeks with RO water and with the last water tests I always have 0 ppm on ammonia and nitrates.

Would be nice though if someone is aware of any source of information for this specific aquasoil.
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post #4 of 8 (permalink) Old 05-05-2019, 02:56 PM
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You can try the 2dKH and see if the soil does remove carbonates.
If it doesn't then you don't need to consider saturating the soil with carbonates.


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post #5 of 8 (permalink) Old 05-05-2019, 03:07 PM Thread Starter
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That's very interesting information that I wasn't aware of... I tried already and the KH felt in 1 in less than a day, do you think is because of that?

The weird thing is that also the GH felt to 1 while I was expecting to be at least 2+.. I am going to try this again to plain RO water and post the results. Are you aware then in any alternatives?
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post #6 of 8 (permalink) Old 05-05-2019, 03:34 PM
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It is possible what you have is a buffering substrate.
Normally chosen to keep pH & alkalinity low.
And why not, plants thrive in it.

What are the requirements of the livestock that will be providing your N & P?


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post #7 of 8 (permalink) Old 05-07-2019, 03:40 AM
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Quote:
KHCO3: 7 grams (yields) => 28 ppm Κ + 2 dKH
MgSO4: 5 grams => 5 ppm Mg + 7 ppm S + 1.2 GH
CaSO4: 10 grams => 10 ppm Ca + 8 S + 1.5 GH
CaCl2: 5 g => 5 ppm Ca + 9 ppm CI + 0.8 GH

So, we have:
2 KH
3.5 GH
28 ppm K
15 ppm Ca
5 ppm Mg
9 ppm Cl
Add to that list:
9ppm Cl
8ppm S

In my opinion to meet your goal you should avoid large excess in nutrients. K is very high and Cl and S are alwo at levels that are way in excess of need. On your list K,S, Cl are the primary drivers of PH. K pushes it up, S and Cl push it down.

Also based on the nutrients found in leaves of plants 10ppm of NO3. S (2,62 N) will cause the plant to want about:
1.744 ppm K
.87246 ppm Ca
.3493 ppm Mg
.3493 ppm P
.17449 ppm S
.01745 ppmCl

Note these vales are approximate There is some variation for different types of plants so some variation should be expected. But 28ppm K would require about 42ppm of N. So if you dose once a week for a month without a water change your going to end up with about 108ppm of K in the water. That much K nay not be good for your plants or fish. S after a month would be around 45 times the need.

IN my RO tank i don't add any KH to my water. It normally stays at about 20ppm and my ph is stable. So you may want to try going without KH to see if your PH stays stable. You could also reduce the potassium level by using a mix of sodium bicarbonate and potassium bicarbonate. Plants don't need the sodium but animals do need some. If you find the tank needs some KH I would only add it when needed.

You could possibly address the excess sulfur and chlorine by adding a mix of calcium and magnesium carbonate. This doesn't dissolve in water with a PH of 7 or more. but in water with a PH less than 7 iSo when CO2 is on it will dissolve You will however have to careful. Add too much and your GH will increase too much. So you could add calcium magnesium sulfate initially and then only add calcium magnesium carbonate as needed to maintain stable GH .

I haven't tried operating my tank this way so these ideas may not work well . But i they do it could help you maintain the tank for longer periods of of time..I would recommend you monitor GH and KH nitrate and phosphate and iron with test kits. If iron gets too high reduce the dose of micros. add nitrate and phosphate and KH and Gh as needed. Hanna instruments sells very good iron and phosphate checkers. Each costs $50 and have a digital readout. They also sell a alkalinity a checker that measures in ppm. Unfortunately they don't sell a nitrate checker.
https://hannainst.com/hi717-phosphate-hr.html
https://hannainst.com/hi775-alkalinity-freshwater.html
https://hannainst.com/hi746-iron-low...eckerr-hc.html
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post #8 of 8 (permalink) Old 05-14-2019, 11:02 PM Thread Starter
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Hi Surf,

Thank you for your very explanatory post. I think in this case I can aim for 1dKH which will yield 14 ppm K in my water which I guess it will be fine for my needs. Soon I will get my PH and TDS monitor and I will follow up my PH to see if I will need more KH.
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