Q: Making a 5dKH solution

mike

Guru Class Expert
Jan 13, 2012
169
0
16
Quebec, Canada
My 125G tank is almost at the end of a dry start and I will be flooding it soon. For a few weeks, before I add fish, I want to maintain a high CO2 level by making a 5dkh solution and making sure it’s always yellow. I already have a 40dkh stock solution. I assume if I add 10ml of 40dkh solution to 350ml of distilled water I will end up with a 5dkh solution, it that correct?

Mike
 

Gbark

Guru Class Expert
Jun 15, 2009
266
1
18
not sure if that would make 5dkh

try adding 50ml of 40dkh to 350ml demin :D
 

Gbark

Guru Class Expert
Jun 15, 2009
266
1
18
If your not adding fish etc for a month or so after flooding it, just whack the co2 right up on the needle valve and dont bother with drop checker. Just remember to bring it down to safe levels before adding fauna. :D

Any pics of your dry start?
 

slowly

Junior Poster
Dec 4, 2012
8
0
1
Texas
Mathe

Oh I hope no one objects, but I don't really get behind math all that much...I don't understand how a person has 50ml of a solution that is 40dkh to be mixxed in a volume of water that is 350ml. to produce a 5dkh solution. Now that is what I believe is being said...How does this math work out????? I'm lost and really want to understand it. any help is appreciated. :eek:
 

mike

Guru Class Expert
Jan 13, 2012
169
0
16
Quebec, Canada
Well, you have a 400ml solution (350ml H20 + 50ml of 40dKH) 1/8th of that solution 400/50 is the 40dKH solution. So the 40dKH solution is only 1/8th as strong 40/8=5dKH.

hope that helps

Mike
 

slowly

Junior Poster
Dec 4, 2012
8
0
1
Texas
Making 5dkh solution

Thanks for the information Mike, and I'm surprised that's all there is to it...I was try in my mind to make it complex and that made it confusing. Thanks again Larry
 

slowly

Junior Poster
Dec 4, 2012
8
0
1
Texas
Making a 5dkh solution

Sorry for being a little late on the up take, but here is where my math dumps me...I assume to have a 4dkh solution in a volume of 50 mils and don't know how to make a solution of 5dkh...How would I know the volume to mix of water to give me a 5 dkh solution? slow.
 
Last edited by a moderator:

mike

Guru Class Expert
Jan 13, 2012
169
0
16
Quebec, Canada
You can't get a 5dkh solution from a 4dkh solution. I'm using a 40 dkh solution and diluting it to give me 5dkh. You have to start with a soluiton that is greater than the solution you want to achieve.

For example. If I want to use 50ml of the 40 dkh solution to make a 4 dkh solution.

40 dkh/4 dkh =10 or 1/10th the strength. Multiply the volume of the 40 dkh solution by 10 (50ml x 10), that gives you 500ml. So I have to mix 450ml of H2O with 50ml of 40 dkh to give me a 4dkh solution.

Same calculation for a 5dkh

40/5=8 or one eight. If I want to use 50 ml of the 40 dkh solution I multipy 50 x 8 = 400ml. So I need to use 350ml of H2O and 50 ml of 40 dkh solution.

You really have to make a 40 dkh stock solution to work with.

I followed these instructions to make my 40 dkh solution.

http://www.plantedtank.net/forums/showthread.php?t=42429

Mike
 

slowly

Junior Poster
Dec 4, 2012
8
0
1
Texas
Making 5dkh solution

I find myself wondering if I have the skills to make these solutions when I find myself just grabbing the math you provided in detail (I want to thank you for such a detailed description), yet I followed the link and it mentions a solution that I googeld to find it means a phenolphthalein (cannot pronounce this word). I want to use co2 in my tank and need the solutions for dc. But honestly this stuff looks scary, and I do have confiedence your site can be of help for me...but I tend to frustrate others and myself at time.......... Slow
 

Darkblade48

Guru Class Expert
Dec 16, 2009
147
0
16
You do not need to use phenolphthalein...

You need to make a 4 (or 5) dkH reference solution, and then add bromothymol blue. This is an indicator that causes the colour change (from blue to green to yellow).

Hope this helps,
 

mike

Guru Class Expert
Jan 13, 2012
169
0
16
Quebec, Canada
Darkblade48;91554 said:
bromothymol blue

Slowly,

In case you were not aware, this is the drops you use to check the PH of your water. I usually add 6 drops to 5ml of 4 or 5 dkh solution.

Mike
 

Yo-han

Guru Class Expert
Feb 6, 2011
285
0
16
Netherlands
slowly;91537 said:
Sorry for being a little late on the up take, but here is where my math dumps me...I assume to have a 4dkh solution in a volume of 50 mils and don't know how to make a solution of 5dkh...How would I know the volume to mix of water to give me a 5 dkh solution? slow.

You need to remove 20% of the water:p Heat the 4dkh solution till 20% is gone or just wait for a long time till it evaporates.
 

Gerryd

Plant Guru Team
Lifetime Member
Sep 23, 2007
5,623
22
38
South Florida
Hi,

You know that you can purchase a solution instead and save yourself all of the time and anxiety.....

I did it when first learning about DC and c02 and the like. Don't feel bad about it either..

Simply purchased it off the web for a few $....
 

slowly

Junior Poster
Dec 4, 2012
8
0
1
Texas
Thanks for your help

I'm just getting back to the site and answer your posts, and will see about getting bromothymol blue, and not looking for the other product. Larry
 

slowly

Junior Poster
Dec 4, 2012
8
0
1
Texas
Why remove 20% using evaporation?

Yo-han;91583 said:
You need to remove 20% of the water:p Heat the 4dkh solution till 20% is gone or just wait for a long time till it evaporates.

Forgive me yo han for not understanding, but why must it be heated to evaporate of 20% of the solution you make...I don't understand this...slow
 

slowly

Junior Poster
Dec 4, 2012
8
0
1
Texas
Maybe I get it?

Yo-han;91583 said:
You need to remove 20% of the water:p Heat the 4dkh solution till 20% is gone or just wait for a long time till it evaporates.

If I have a solution of 4dkh and evaporate off 20% of the volume it will remove water not chemicals so make the solution stronger...Hope I not just grooping around in the dark with this idea...wouldn't be the first time. slow
 

Darkblade48

Guru Class Expert
Dec 16, 2009
147
0
16
slowly;91770 said:
Forgive me yo han for not understanding, but why must it be heated to evaporate of 20% of the solution you make...I don't understand this...slow

slowly;91772 said:
If I have a solution of 4dkh and evaporate off 20% of the volume it will remove water not chemicals so make the solution stronger...Hope I not just grooping around in the dark with this idea...wouldn't be the first time. slow

Yes, this is correct, but it is easier to just make a stock solution of (say) 40 dkH and make dilutions from there rather than trying to re-concentrate something.
 

Left C

Lifetime Members
Sep 26, 2005
2,500
1
36
72
Burlington, NC
A fairly cheap kit to test the accuracy of your dKH solutions is LaMotte's KH/Alkalinity test kit. It works great! It has a beginning color and an endpoint color. And, if you add just a little too much, it gives you a "past" endpoint color. This is a nice feature that is not found with API's, Hagen's Tetra's, and many more "hobby grade" test kits. You can also get refills for it too. It measures in ppm instead of dKH. So, you'll have to do a conversion. There are 17.86 ppm in 1 dKH. So, 4 dKH would be 71.44 ppm.

instructions for use