Remineralizing RODI

[techman81]

Ashamed to admit this, but after decades in engineering, I know longer enjoy doing math. Hmm, did I ever really enjoy it? Anyway, I've reached the point in life where I prefer the easy way out. So after reading numerous articles and @Naturescapes_Rocco 's post on remineralizing, I'd like to be able to put together a simple chart that just tells me how many teaspoons (or mg if I must) of Calcium Sulfate/Chloride and Magnesium Sulphate to add to a given amount of fresh RODI water after a water change to go from 0 gh to 7 gh. Basically something like the APT Sky dosage calculator on the 2HR Aquarist site. After adding, say 22 gallons of RO water, I can look at the chart and it tells me 2 3/4 tsp of this and 1 1/4 tsp of this. Rocco's post mentioned the calculator on Rotala Butterfly but after looking at it, I'm not sure it does what I'm asking, or maybe it does and my brain is just mush today. Up to now I've been using APT Sky, but want to start saving a little money where I can. Eventually, I'll be dropping the APT 3 and doing the DIY ferts as well.

 

[Naturescapes_Rocco]

No worries, we got you! The markup on GH Remineralizers is insane. Once you make your own, you'll never go back. It is insanely cheap.

Here's the gist how:​

Use CaSO4 and MgSO4 powders to remineralize your RO water to ~30ppm Ca and ~7ppm Mg. Do this by measuring the powders on with a small "jewelry" scale ($15 on amazon or less). Add to your tank after adding the RO water, and you're done.

Here's a more in-depth answer:​

1. You'll need to know how many gal of RO water you're adding. Let's say you're adding 20Gal of RO water after your WC (I like to mark the known line on the side of my aquarium with a sharpie)...
2. GH is made up of Calcium and Magnesium. I'd suggest aiming for a slightly lower GH, no need to go as high as 7 unless you worry about specific inhabitants. For a GH of ~6, you'll want to remineralize your RO water to 32ppm Ca and 7.5ppm Mg.
3. To add Ca, use CaSO4*2H2O, aka Gypsum. I buy mine in bulk from Nilcog, $18/5lb:
   
   To add Mg, use MgSO4*7H2O, aka Epsom Salts. I buy from the same vendor.
4. Use Rotala Butterfly like so. I've highlighted all the inputs you'll have to add manually:
   

There you have it! To raise 20 gal of RO Water from 0ppm to 32ppm Ca, you need to add 10.4g of CaSO4.

Measure 10.4g Gypsum with your small scale (here's one I use), and dose into your tank.

Side note about CaSO4/MgSO4 solubility:​

MgSO4 is a great dry salt. It's usually sold as small crystals that are easy to weigh, and dissolve easily in the tank.
CaSO4 is an annoying dry salt. If you dose dry clumps into your tank, they can form clumps underwater than can take up to 36 hours to dissolve.

This can be mitigated if you dose into moving water, into a filter directly during water changes, or any other methods you can think of.

Personally, I keep a rechargeable milk frother with a small glass mason jar with my tank's water change equipment. After I've replaced the tank's water with pure RO water, I fill the jar halfway with RO water, and dose the CaSO4+MgSO4 directly into the jar, then mix for 5s with the milk frother. You don't need to dissolve the CaSO4, just hydrate it, and it won't be a problem to dissolve in your aquarium. Pour this into your aquarium and you're good, no clumps!

 

[Naturescapes_Rocco]

For reference, you would need about 9g of APT Sky to raise your Ca by 30ppm and Mg by 9ppm (GH~6). The small pouch of APT Sky costs about $0.10/gram, so every water change costs you ~$1 of APT Sky to remineralize 20Gal RO Water.

If purchasing the salts I listed above $18/5lb, and doing it DIY, it would cost you ~$0.10 to remineralize 20Gal RO water. Almost 1/10th the cost for just a little more work.

For small tanks and beginners, I personally recommend APT Sky, but for anyone who is going to spend enough time in this hobby (or with larger tanks) learning how to use Rotala Butterfly and CaSO4/MgSO4 powders is easy and will save you lots of money immediately for the same or similar results, with full control over your dosing, too.

 

[Koan]

No worries, we got you!

 

[techman81]

No worries, we got you! The markup on GH Remineralizers is insane. Once you make your own, you'll never go back. It is insanely cheap.

Here's the gist how:​

Use CaSO4 and MgSO4 powders to remineralize your RO water to ~30ppm Ca and ~7ppm Mg. Do this by measuring the powders on with a small "jewelry" scale ($15 on amazon or less). Add to your tank after adding the RO water, and you're done.

Here's a more in-depth answer:​

1. You'll need to know how many gal of RO water you're adding. Let's say you're adding 20Gal of RO water after your WC (I like to mark the known line on the side of my aquarium with a sharpie)...
2. GH is made up of Calcium and Magnesium. I'd suggest aiming for a slightly lower GH, no need to go as high as 7 unless you worry about specific inhabitants. For a GH of ~6, you'll want to remineralize your RO water to 32ppm Ca and 7.5ppm Mg.
3. To add Ca, use CaSO4*2H2O, aka Gypsum. I buy mine in bulk from Nilcog, $18/5lb:
   View attachment 12435
   To add Mg, use MgSO4*7H2O, aka Epsom Salts. I buy from the same vendor.
4. Use Rotala Butterfly like so. I've highlighted all the inputs you'll have to add manually:
   View attachment 12437

There you have it! To raise 20 gal of RO Water from 0ppm to 32ppm Ca, you need to add 10.4g of CaSO4.

Measure 10.4g Gypsum with your small scale (here's one I use), and dose into your tank.

Side note about CaSO4/MgSO4 solubility:​

MgSO4 is a great dry salt. It's usually sold as small crystals that are easy to weigh, and dissolve easily in the tank.
CaSO4 is an annoying dry salt. If you dose dry clumps into your tank, they can form clumps underwater than can take up to 36 hours to dissolve.

This can be mitigated if you dose into moving water, into a filter directly during water changes, or any other methods you can think of.

Personally, I keep a rechargeable milk frother with a small glass mason jar with my tank's water change equipment. After I've replaced the tank's water with pure RO water, I fill the jar halfway with RO water, and dose the CaSO4+MgSO4 directly into the jar, then mix for 5s with the milk frother. You don't need to dissolve the CaSO4, just hydrate it, and it won't be a problem to dissolve in your aquarium. Pour this into your aquarium and you're good, no clumps!

I knew you would come through.
1. I use a flow meter on the hose I refill the tanks with from the RO storage tank so I always know exact volume I've added.
2. I used 7gh only because my tanks have shrimp and snails, but I could probably drop to 6.
3. I bought the powders on Amazon months back but was using up the APT Sky I had before switching over. That time is getting close.
4. Your math is a little clearer for me in this post than the other I read. From this I think I can now create a chart to tell me how many tsp of each powder per gallon.

Thank you!

 

[Pepere]

Eventually, I'll be dropping the APT 3 and doing the DIY ferts as well.

Using dry salts to make your own macros and micros saves an incredible amount of money.

I do 66% water changes weekly on my tanks and then frontload to get back up to baseline. So in essence I dump out about half of my fertilizer amounts weekly…

In any event I figured out that it costs me $1.02 be month to fertilize a 75 gallon tank……

I started calculating the cost of my fertilizer after reading about so eone insisting Val, Crypts, Amazon Sword and such are “Heavy Root Feeders” and must be fed root tabs to see them healthy and grow…. And they mentioned they sink 4 root tabs per amazon Sword Monthly. That works out to 1.47 for 1 freaking sword per month in addition to their WC ferts…

I just use 1.02 for an entire tank…

 

[techman81]

For reference, you would need about 9g of APT Sky to raise your Ca by 30ppm and Mg by 9ppm (GH~6). The small pouch of APT Sky costs about $0.10/gram, so every water change costs you ~$1 of APT Sky to remineralize 20Gal RO Water.

If purchasing the salts I listed above $18/5lb, and doing it DIY, it would cost you ~$0.10 to remineralize 20Gal RO water. Almost 1/10th the cost for just a little more work.

For small tanks and beginners, I personally recommend APT Sky, but for anyone who is going to spend enough time in this hobby (or with larger tanks) learning how to use Rotala Butterfly and CaSO4/MgSO4 powders is easy and will save you lots of money immediately for the same or similar results, with full control over your dosing, too.

Well, I just learned I've been throwing even more money out the window than I needed to.

After looking at your Rotala Butterfly calculated image, something seemed off. I already had a gram scale (the same you listed in fact) that I've used for years for measuring remineralization of RO water for homebrewing (yep, there's sites with calculators for that too). The image showed about 10.5 grams equivalent to about 3 1/4tsp. I measured a tsp of calcium sulfate on my scale and it was over 5g (calibration was perfect and a different brand/model of tsp was about the same). So if I went by my tsp, I'd be dosing 45% higher than Rotala Butterfly's calculated weight. Out of curiosity, I decided to check the APT Sky calculator and guess what, I've been dosing 45% more of that as well.

I've always heard that in baking, the pros say to measure your ingredients by weight rather than volume. I now get it. Interestingly, I did always go by weight when homebrewing. I guess I'll need to stick to grams on my quick read chart.

 

[Naturescapes_Rocco]

If you do the same volume of water change, you can prepare dry salts weeks in advance in one sitting:

Makes it easy!