kekon

I know this topic was discussed by thousands of people many times but i'm somewhat confused.
I always used RO water reconstituted by different chemical compounds. There some recommendations concerning of how much calcium and magnesium should be in the water used for aquatic plants we grow in our tanks. For examaple, Seachem says that GH of 3..6 dGH is optimum. In literature i read that 6..10 dGH should be used. The "Fertilator" recommends 20..30 ppm of Ca. In turn, T.Amano keeps extremely soft water in his tanks (is it because some of ADA products PenacW or PenacC contains plenty of CaCO3 ?). In one of his interviews he said soft water is preferred by plants and they grow better when such conditions are met. Very soft water can lead to calcium deficiency very often but many people managed to grow great plants even in GH = 2..3. What do you think about it ?

OTPT

kekon

But they also wrote:

If i get it correctly, if one mixes tap water of GH 15-20 with RO water in 4 to 1 ration then one obtains GH of 3..4. So it is unclear... 6..8 or 3..4 ?

Michael

I don't think this question can be answered unless we know which species are being considered. Different species have different preferences.

Seattle_Aquarist

Hi kekon,

When Tom Barr was in Seattle and did his presentation for GSAS I asked what hardness he recommended for growing most plants. He said he targeted a 5.0 dGH and didn't worry about his dKH.

OTPT

I expected you notice this. And I'm also a bit confused about it.

But why they advise starting with 6-8? Maybe they're afraid of too soft water also.

Either way, this surprises and also satisfies me in someway, I thought it was lower than this.
Now it's not incredibly low anymore.

BTW, I've just found the reliable source of info saying Brighty K is made from Potassium Carbonate.
May be they use that to counteract Aqua Soil.
http://www.adana.co.kr/product2.asp?seq=21 (please use Google translate)

kekon

Potassium Carbonate or Potassium Bicarbonate ? (K2CO3 or KHCO3 ?). The first one is extremely basic; i had problems with it. But KHCO3 worked well. K2CO3 caused stunting and precipitation of CaCO3 (water got cloudy in the tank)

OTPT

탄산칼륨 = K2CO3
http://ko.wikipedia.org/wiki/탄산_칼륨

I thought about this too as I have read your thread about KHCO3.
Don't have any comment though, I'm not Korean nor a chemist.

Diana K

Most plants that we grow in our aquariums are quite adaptable to a wide range of GH, as long as it is not 0. They do need both Ca and Mg to survive.

There are a few specialty plants that do not do well in water with too high mineral level. If you are growing any of these plants research and keep the parameters right where they need them.

There are quite a few plants that can get the carbon they need from carbonates, if the CO2 is lacking. For these plants a KH over about 3 degrees is better. Usually, though, KH is used as a buffer when adding CO2, so the pH does not swing wildly high and low through the day.

kekon

A few days ago a friend of mine forgot to add NaHCO3 when he reconstituted RO when doing water change. pH in his tank was decreased to 6.2. When that happened his plants started to grow better; Rotalla Walichii which was problematic plant now is growing quite well. Is it because of zero KH or low pH ? From what i know plants prefer slightly acidic water as micronutrients are better taken up by plants (especially iron and manganese) in lower pH.