Thank you Mr Tom, I was breaking my head with water parameters and mixing RO water with tap water. Here in Canary Islands we have very hard water and most people in the hobby have truble bringing down the hardeness

About ammonia and ammonium, the last one is the one escreted in urine, but as a weak acid it wil be a bad donor of protons. Although at a higher pH will increase the formation of ammonia, In a resonable pH interval for our aquarium, I would guess that it won´t mean much. Also you have to consider all of the ammonia removal by bacteria and plants.

From wikipedia (I don´t have time to calculate myself) at pH 7 99% of ammonia would protonate into ammonium.