RO water Seachem and Discus

[Lionel]

I wish I could understand better which seachem products to use in order to treat RO water for my discus tank.
I'd like to get KH=GH=2 and pH 6.0.
Equilibrium, discus buffer, acidic buffer+neural buffer....???? I'm confused.
Many thanks

[Tech Support CH]

To raise your GH use Equilibrium.

PH and KH rely on each other so you can not adjust them separately of each other. Your pH is a result of your KH and CO2 level. To achieve a 6.0 pH with a 2 KH you will need to add a lot of CO2. I would recommend that you either chose a pH to target or a KH to target. Most people that have a 2 KH and do not inject CO2 will have a pH around 7.2-7.4.

If you don't mind using a phosphate based buffer I would recommend Discus buffer as it is a very stable buffer and can hold your pH level.

[Lionel]

Many thanks for you answer, but I would like to discuss further this question because probably my question was not clear.
First of all, if, as you say, pH relay KH, it is true only partially. pH I proportional to [H3O]+ and that’s it !
It is possible to have pH 4, 5, 6 a KH 2; it depends how much acid (i.e. CO2 into the tank) one use, but does not chemically correlates to [CO3].
Actually my question was another one: I asked how to prepare RO water to bring it at KH2 and pH 6 not into the tank but when I prepare it.
So, for this purpose, I need first to “buffer it” at KH 2 and then to acidify it a pH 2 since “non phosphate buffer” do not allow to have acidic pH.
So: which seachem products can I use to get such values ???
Many thanks again.

PS: I would exclude phosphate buffer if possible

[Tech Support CH]

To get a pH of 6 and a KH of 2 you will need to add enough Alkaline Buffer to attain that KH. Then you will need to inject CO2. That high of CO2 will also dissolve away your KH. So you will need to add back Alkaline Buffer to maintain your KH. There is no way around it without using phosphate. Be careful adding this water to a fish tank because the high CO2 levels can harm or kill the fish.

To raise your GH you will want to use Equilibrium.

[Lionel]

OK, many thanks again !
So you recommend using phosphate buffer !
Is ti possible to quantify the amount of PO4 that this buffer would generate into the tank ?
Would it be deleterious for plant and/or algae ?

[Tech Support CH]

I do not recommend Phosphate based buffers for most plant tanks. Phosphate will precipitate out calcium, magnesium, and iron. All of which are nutrients required by plants. Some soft water plants would go fine in this environment. Also if you have additional light for your plants the high phosphate combined with other nutrients (like nitrate) can encourage algae growth.

In your case I would either choose to keep the water at a higher pH or a lower KH. And use Acid Buffer and Alkaline buffer to set it to the desired pH or the desired KH.

There are many CO2/pH/KH charts on the internet. I would recommend that you do a search and that will help you be able to set the levels better. On plantgeek.net they have a very good CO2 chart under their Resources section. They even have an area that you can plug in your pH and your KH and it will tell you your CO2 level. To attain a pH of 6.0 and a KH of 2 dKh you will need a CO2 level of 60 ppm.

[petros]

Hello there! I have a 200lt discus tank densily planted with Co2 injection.The pH level was 6.6 for a long time and suddenly begun to decrease.It reached a value of 6, but I found a way to raise again to 6.6. However I believe it will decrease again due to zero KH and CO2 injection. I use 100% RO water cause the tap water has very high pH level (over 8). What should I do or add to raise the KH and consequently stabilise the pH? The phosphates do not worry me very much cause I use resin pouch to remove them. Thanks for your time

[Tech Support CH]

To raise your KH I would recommend Alkaline Buffer. Since you are using RO water, if you wish to target a certain pH I would recommend to use both Acid Buffer and Alkaline Buffer together in the ratios listed on the label.

I would also recommend that you add Equilibrium to raise your general hardness (GH). Plants need this calcium and magnesium to grow properly.