Hard Water

[bricast]

Need help!!  I setup a fish take with distilled water and after a few weeks the water became extremely hard.  I have replaced more then 20% of the water.  I have used different chemicals for making "tap water" safe for fish event thought I did not use tap water.  I recently also added a water softener pillow in my filter.  Can anybody tell me why my water is so hard.  The test strips say that the Nitrate (NO3) is 0, Nitrite (NO2) is 0, PH is 6.5 Carbonate Hardness (KH) is 40, and General Hardness (GH) is off the cart over 180.

 

[BaylorPerez]

You may want to see what distilled water you added to the tank, I know my LFS has distilled water with a GH of 30

 

[AbbeysDad]

Although you should probably test the 'distilled' water, I wonder about the reliability of your test results. Distilled water should be as soft as water can be since there are no minerals at all (unless it's been adjusted). Otherwise, there may be something (decor) in your tank that is altering the water chemistry (rocks, coral, gravel...). You could selectively test any of these by placing individually in a small bucket or bowl with with distilled water and testing after a day or two. 
 

 

[Zante]

Agreed. I'd check if you have something in your tank that is leeching minerals. Take some gravel/sand out and the rocks and put some vinegar on them. If they start fizzing a bit then they are calcareous and dissolving in your soft water.

 

[StevenF]

When I set up a RO system at my sisters house I used tetra 6 in 1 strips to check the hardness of her water and the output of the RO system.  Later she got a GH test done by a lab.  The lab reported 280ppm, The test strip color chart was a close match to 300ppm.  The RO water tested at 25ppm (which is what one would expect for RO water)  For GH the strips I used were accurate.  
 
Tetra Easy strips should be put in the water vertically for 1/2 second and then removed very rapidly (yank it out).  If done the correct way i find you get accurate results.
 
Fish food contains many minerals in it.  If you don't cycle water out of the tank on a weekly basis the fish food will make it hard.  Normal routine maintenance for an aquarium is to remove 30 to 50% of the water and then add dechlorinated tap water or distilled / RO water to replace the removed water.  If that was done water hardness would not reach 180.  Water evaporation accelerates the GH increase.
 

 
 
I setup a fish take with distilled water and after a few weeks the water became extremely hard.  I have replaced more then 20% of the water. 

Based on that I suspect you only added water to replace what evaporated and haven't cycle any water out or not enough to keep GH stable.