calcium deficiency problem?

["pieter cool" <pieter.cool at esat_kuleuven.ac.be>]

Hello,
 
My problem is the following.
My swordplant's new leaves are almost white. The new leaves are also a little curled.
I think it is a Ca problem.
What I don't understand is that my Kh and Gh are about 10 dH.
When I do waterchange I do it with water that has a Kh and Gh of almost 0
dH. 
My tapwater has a Gh of 27dH and also a very high Kh. To lower these values I use an ion-exchangers.
I think that there's an exchange , the Ca and Mg to Na.
The strange thing is that the water in the tank stays at 10 Gh and Kh.
Perhaps it is the substrate  I use in the tank. Perhaps it releases
chemicals other than Ca in the water that
higher the Kh and Gh .
Or there might be shells in the substrate that release Ca in the water. 
When this is the case , I don't understand the problem of my swordplant.
An other thing I've noticed is the shell of the snails. I can almost look through it.
This also looks like a Ca deficiency to me.

If someone could help me with this , I would be very gratefull.
Excuse me for my bad English but I'm from Belgium.

Thanks
Pieter




--- StripMime Report -- processed MIME parts ---
multipart/alternative
  text/html
---