Re: RO water + minerals

Andi (hermel at ibm_de) wrote:
> I use 25 liters RO water and 5 liters of tap water.

This sounds fine based on the data you gave for tap water.

> In the future, I probably will only use RO water to keep the nitrate (which
> is 15 mg/l in the tap water) and the KH which is 15 and all the other stuff 
> like pesticides out of the tank.

It's not necessary to completely eliminate nitrate from your water changes.
Many of us add nitrate along with other nutrients in PMDD and achieve good
results. I note that you have very low lighting intensity however so
I would not suggest supplementing nitrate except for what's in the
5 liters of tap water. I doubt if there are pesticides in your tap water
(if it is drinkable...)

> 2) As long as I add some tap water, could that be the source for missing 
>    elements? How much tap water would I need for it? (Although I don't want
>    to use tap water really...)

If you get a water analysis from your water utility, there is no reason
not to take advantage of some of the minerals present. Why not contact
the water utility? Here the analysis is provided free and they are very
willing to chat with anyone on the phone. (must not be too busy ;-)

> 3) At the moment my KH is 4 and the GH is 8 
>    What level of KH should I aim for? I use PH-controlled CO2 injection,
>    PH is 6.8, CO2 is 20 mg/l.

These levels are fine.

> 4) Do I have to raise the GH also? 

GH is misleading. Instead ensure that you have sufficient calcium and
magnesium which are the primary contributors to GH. Avoid rapid changes
in the water parameters. I'd settle on your water change method
and then stick to it. I don't think you will have problems with
copper with your hard water (but check the analysis)

> Or does GH increase with the KH?


> Some plants (especially the rotalas) still lose 1 or 2 lower leaves every day. 
> But maybe they are planted too close so that the lower leaves don't get 
> enough light, I am not too sure about that. I have 30 watts + reflectors for
> the 27 gallon tank.

You said you have a triton and a neon light in a previous message.
I do not think you have enough light for Rotala. If it's possible for
you to use T-8s, you could use two of those to get adequate lighting
or 3 to get good lighting. I don't know how efficient a neon light
is but I would replace it. The long term operating costs of electricity
will outweigh the costs of upgrading to T-8s I think. I also had
poor Rotala growth with very strong MH lighting, but I was N limited.

> Fe is 0.7 mg/l although I use 150% of the recommended dose of Dupla-24 everyday.

This is more than sufficient Fe. You said before you were going to aim
for 0.1 mg/L weren't you?

I think you need to up the light levels a bit Andi and then see how
your nutrient levels stabilize.

Steve in Sunny Vancouver