Reef Chemistry Calculator Question

Reef Chem · 01/30/2017, 08:32 PM

Hello all,

I have a question on the reef chemistry calculator (http://reef.diesyst.com/flashcalc/flashcalc.html), hopefully that works or you at least know the calculator I'm talking about. Anyways, I have a nano reef tank and also have a freshwater tank. I have well water which is not very good for either. Therefore, I solely use RO/DI for my reef tank and RO for the freshwater. For my freshwater I am little confused on what I am aiming for compared to what my test state (in regards to GH). I know this is a marine forum but I think someone could help. For calcium I am trying to go from 0 to 40ppm with Kent Liquid Calcium so it says to use 7.5ml and for the magnesium I am going from 0 to 10ppm with Kent's Tech M and it says to use 2.7ml. From what I understand GH test for calcium and magnesium so the total of 50ppm should put me around 3 or 4dh, however, when I test the GH I am getting 10dh as a result. Any thoughts why this is? Sorry if this is too freshwater related with GH and all but I enjoy both and there is not a lot on freshwater forums for what I am doing. Please let me know if you need any more details.

Thanks

Reef Chem · 01/30/2017, 08:46 PM

Sorry, forgot one important detail. I am mixing 5 gallon buckets so that is "system water value" I am using to base how much of each product to put in.

nicholasb · 01/30/2017, 09:37 PM

GH is general hardness or total alkalinity (measured in meql). It is total hardness/buffering of the water, and includes carbonates, bicarbonates, borate, phosphate, and silicate. DKH is the hardness due to carbonates and bicarbonates only (measured in dkh). Calcium and magnesium have nothing to do with GH. I don't know what you should aim for. Make sure you uses a test kit that works in fresh water and not a marine only test kit..

bertoni · 01/30/2017, 10:46 PM

From my reading, dGH is a measurement of the calcium oxide (or its equivalent) in the water. 1 dGH is about 10 ppm CaO. The molecular weight of CaO is about 56, and Ca is about 40 for atomic weight. So the 40 ppm calcium you added was about 56 ppm CaO equivalent.

The atomic weight of magnesium is about 24, and the molecular weight of magnesium oxide is about 40. The 10 ppm of magnesium is about 16.7 ppm magnesium oxide equivalent, or about 23 ppm calcium oxide equivalent.

So I get 80 ppm CaO equivalent, which I would have thought would be 8 dGH.

Potatohead · 01/31/2017, 12:29 AM

What fish are you keeping? Fish in soft water like South American cichlids can be around 3-5 gh. Africans need more like 12-15 or even higher, and the rest in the middle.

The easiest way to raise kh and ph in freshwater is with baking soda (sodium bicarbonate). The easiest way to raise gh (and nothing else) is with epsom salt (magnesium sulfate).

I keep a 210 gallon with a colony of Zaire Frontosa. My water out of the tap is extremely soft, virtually no buffering capacity. I do water changes of 80 gallons per week and to that 80 gallons I add 3/8 cup of baking soda and 7/16 cup epsom salt. This keeps the ph around 8.2 and both kh and gh are about 12-14.

Reef Chem · 01/31/2017, 11:38 AM

Thanks for the replies. My freshwater is just simple tropical fish (tetras, gouramis, platies, etc.) that would probably be fine in between soft and hard water. So a GH of 10 is fine with me I was just trying to figure the math out but that seems pretty complicated. For the KH I also use baking soda. I mix 1/2 tsp per 5 gallons and that comes to 5 kh which is consistent with what the reef chemistry calculator says it should be. That is why I was questioning the GH.

I thought you needed a 4:1 or 3:1 Ca to Mg ratio, if you use only epsom salt wouldn't that mean there is no Ca being added? That is what got me started on this whole issue. I used to dose equal parts of Ca & Mg (according to the chemistry calculator) and then I decided to research it again to see if I felt any different and decided to try a 4:1 ratio opposed to 1:1. Even with the 1:1 ratio I was using I noticed the GH was harder than I thought it should have been according to the chemistry calculator.

The test kit I use is just a basic API freshwater GH test kit. I thought GH test kits were essentially testing Ca & Mg since that is the majority of the general hardness even though I believe there are other factors within GH. I'm guessing bertoni's math might be why the test reads higher than what I expected it just a little complicated for me. =)

Potatohead · 01/31/2017, 12:06 PM

I never looked into it that closely. I have been doing it this way for 3.5 years and I wouldn't say my Fronts have any lack of color or growth. The only other thing I do add is Seachem Cichlid Trace, 20 ml to 80g of new water. I also do have a bunch of crushed coral in one of my filters but I believe the pH is likely too high for it to really dissolve and add anything to the water. I could be wrong. I add a very small amount of kosher salt to my mixing barrels as well, but it's only about 1/10 cup.

https://www.youtube.com/watch?v=dGCkJ6z2c14

Looking at that video now it's amazing how much more they have grown in the time since. My large males are huge, lol.

Potatohead · 01/31/2017, 12:34 PM

Hmm, so after doing some reading I may try adding some calcium chloride to my mixing barrels just to experiment and see if I notice any change in the fish. I have lots around from dosing my reef tank. There is some in the Cichlid Trace I use but i'll try a bit more. I'm not sure if an API or Salifert calcium test will test freshwater correctly or not.

Reef Chem · 01/31/2017, 12:46 PM

Nice tank! They look healthy to me. I have had my tank running for about 3 years or so doing a 1:1 ratio with Kent Liquid Calcium and Kent Tech M Magnesium (and baking soda for the KH) and I haven't had any issues. I chose those products since I had them handy for the saltwater tank. I felt like changing it up with a 4:1 ratio since most sites tend lean towards that or 3:1 being an average ratio. I also bought some Seachem Fresh Trace. RO is great but since it strips the water of all good and bad I figured it won't hurt to add some trace elements back in.

bertoni · 01/31/2017, 04:30 PM

Those are beautiful fish!

01/30/2017, 08:32 PM	#1
Reef Chem Registered Member Join Date: Mar 2011 Posts: 84	Reef Chemistry Calculator Question Hello all, I have a question on the reef chemistry calculator (http://reef.diesyst.com/flashcalc/flashcalc.html), hopefully that works or you at least know the calculator I'm talking about. Anyways, I have a nano reef tank and also have a freshwater tank. I have well water which is not very good for either. Therefore, I solely use RO/DI for my reef tank and RO for the freshwater. For my freshwater I am little confused on what I am aiming for compared to what my test state (in regards to GH). I know this is a marine forum but I think someone could help. For calcium I am trying to go from 0 to 40ppm with Kent Liquid Calcium so it says to use 7.5ml and for the magnesium I am going from 0 to 10ppm with Kent's Tech M and it says to use 2.7ml. From what I understand GH test for calcium and magnesium so the total of 50ppm should put me around 3 or 4dh, however, when I test the GH I am getting 10dh as a result. Any thoughts why this is? Sorry if this is too freshwater related with GH and all but I enjoy both and there is not a lot on freshwater forums for what I am doing. Please let me know if you need any more details. Thanks

01/30/2017, 10:46 PM	#4
bertoni RC Mod Join Date: Mar 2002 Location: Mountain View, CA, USA Posts: 88,616	From my reading, dGH is a measurement of the calcium oxide (or its equivalent) in the water. 1 dGH is about 10 ppm CaO. The molecular weight of CaO is about 56, and Ca is about 40 for atomic weight. So the 40 ppm calcium you added was about 56 ppm CaO equivalent. The atomic weight of magnesium is about 24, and the molecular weight of magnesium oxide is about 40. The 10 ppm of magnesium is about 16.7 ppm magnesium oxide equivalent, or about 23 ppm calcium oxide equivalent. So I get 80 ppm CaO equivalent, which I would have thought would be 8 dGH. __________________ Jonathan Bertoni

01/31/2017, 12:34 PM	#8
Potatohead Registered Member Join Date: Apr 2016 Location: Vancouver Posts: 1,596	Hmm, so after doing some reading I may try adding some calcium chloride to my mixing barrels just to experiment and see if I notice any change in the fish. I have lots around from dosing my reef tank. There is some in the Cichlid Trace I use but i'll try a bit more. I'm not sure if an API or Salifert calcium test will test freshwater correctly or not. Last edited by Potatohead; 01/31/2017 at 12:40 PM.

01/31/2017, 04:30 PM	#10
bertoni RC Mod Join Date: Mar 2002 Location: Mountain View, CA, USA Posts: 88,616	Those are beautiful fish! __________________ Jonathan Bertoni

01/30/2017, 08:46 PM	#2
Reef Chem Registered Member Join Date: Mar 2011 Posts: 84	Sorry, forgot one important detail. I am mixing 5 gallon buckets so that is "system water value" I am using to base how much of each product to put in.

01/30/2017, 09:37 PM	#3
nicholasb Registered Member Join Date: Mar 2014 Location: south west england Posts: 292	GH is general hardness or total alkalinity (measured in meql). It is total hardness/buffering of the water, and includes carbonates, bicarbonates, borate, phosphate, and silicate. DKH is the hardness due to carbonates and bicarbonates only (measured in dkh). Calcium and magnesium have nothing to do with GH. I don't know what you should aim for. Make sure you uses a test kit that works in fresh water and not a marine only test kit..

01/31/2017, 12:29 AM	#5
Potatohead Registered Member Join Date: Apr 2016 Location: Vancouver Posts: 1,596	What fish are you keeping? Fish in soft water like South American cichlids can be around 3-5 gh. Africans need more like 12-15 or even higher, and the rest in the middle. The easiest way to raise kh and ph in freshwater is with baking soda (sodium bicarbonate). The easiest way to raise gh (and nothing else) is with epsom salt (magnesium sulfate). I keep a 210 gallon with a colony of Zaire Frontosa. My water out of the tap is extremely soft, virtually no buffering capacity. I do water changes of 80 gallons per week and to that 80 gallons I add 3/8 cup of baking soda and 7/16 cup epsom salt. This keeps the ph around 8.2 and both kh and gh are about 12-14.

01/31/2017, 11:38 AM	#6
Reef Chem Registered Member Join Date: Mar 2011 Posts: 84	Thanks for the replies. My freshwater is just simple tropical fish (tetras, gouramis, platies, etc.) that would probably be fine in between soft and hard water. So a GH of 10 is fine with me I was just trying to figure the math out but that seems pretty complicated. For the KH I also use baking soda. I mix 1/2 tsp per 5 gallons and that comes to 5 kh which is consistent with what the reef chemistry calculator says it should be. That is why I was questioning the GH. I thought you needed a 4:1 or 3:1 Ca to Mg ratio, if you use only epsom salt wouldn't that mean there is no Ca being added? That is what got me started on this whole issue. I used to dose equal parts of Ca & Mg (according to the chemistry calculator) and then I decided to research it again to see if I felt any different and decided to try a 4:1 ratio opposed to 1:1. Even with the 1:1 ratio I was using I noticed the GH was harder than I thought it should have been according to the chemistry calculator. The test kit I use is just a basic API freshwater GH test kit. I thought GH test kits were essentially testing Ca & Mg since that is the majority of the general hardness even though I believe there are other factors within GH. I'm guessing bertoni's math might be why the test reads higher than what I expected it just a little complicated for me. =)

01/31/2017, 12:06 PM	#7
Potatohead Registered Member Join Date: Apr 2016 Location: Vancouver Posts: 1,596	I never looked into it that closely. I have been doing it this way for 3.5 years and I wouldn't say my Fronts have any lack of color or growth. The only other thing I do add is Seachem Cichlid Trace, 20 ml to 80g of new water. I also do have a bunch of crushed coral in one of my filters but I believe the pH is likely too high for it to really dissolve and add anything to the water. I could be wrong. I add a very small amount of kosher salt to my mixing barrels as well, but it's only about 1/10 cup. https://www.youtube.com/watch?v=dGCkJ6z2c14 Looking at that video now it's amazing how much more they have grown in the time since. My large males are huge, lol.

01/31/2017, 12:46 PM	#9
Reef Chem Registered Member Join Date: Mar 2011 Posts: 84	Nice tank! They look healthy to me. I have had my tank running for about 3 years or so doing a 1:1 ratio with Kent Liquid Calcium and Kent Tech M Magnesium (and baking soda for the KH) and I haven't had any issues. I chose those products since I had them handy for the saltwater tank. I felt like changing it up with a 4:1 ratio since most sites tend lean towards that or 3:1 being an average ratio. I also bought some Seachem Fresh Trace. RO is great but since it strips the water of all good and bad I figured it won't hurt to add some trace elements back in.