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Opae Ula Crazed.
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Discussion Starter · #1 ·
Just curious here...

Stupid question, perhaps:

When topping off a tankful of remineralized RO or Distilled water, should one add minerals to the replacement water? Do the minerals in the tank get used up or somehow absorbed/stored by the substrate, plants or critters within a tank?

Thanks!
 

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Opae Ula Crazed.
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1,408 Posts
Discussion Starter · #3 ·
Yeah, with saltwater tanks the salt doesn't evaporate with the water, the specific gravity increases as the water leaves. So topping off with fresh, unadulterated RO or distilled water makes sense.

Guess my question should be:

"Does gh and kh increase in a freshwater tank as the water evaporates?"


Sent from my Samsung Galaxy S III using Tapatalk 2
 

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I'm pretty sure only H2O evaporates, and everything dissolved stays in the body of water.
Top off with RO/DI water with NO minerals added.
+1.

Just top off with RO/DI water. The amounts of minerals that are used up by plants is probably negligible compared to if you were to top off using remineralized water (this would probably increase the GH and KH).
 

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You can test the GH and KH etc through the week. If the plants are using a lot of Ca and Mg, and you find the GH dropping for example, then it is OK to top off with water that adds back just the amount of minerals you need.

However, in my low tech tanks the plants did not use the minerals that fast, so top off with rain water was helpful after using tap water through the summer. TDS climbs through the summer unless I do a really big water change.
 
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