# Kh & Gh



## Cocobid (Jan 26, 2007)

Our new tank is 14T Aquasoil. We are at midweek of a water change cycle. 
I want to put some CRS & CBS. 

Are these numbers good?
Kh 6 Drops to turn yellow and if I read the chart properly 106.4
Gh 9 Drops to turn green, chart reading 161.1

Everything is great ph is around 7.4
No Nitrate, Nitrite or Ammonia.

TY Karen


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## MacFan (Jul 30, 2006)

Divide by 17.9 to get degrees of hardness which is how people in the hobby seem to refer to it most often. So that would be 6dKH and 9dGH. I think that would translate to medium hard water (very hard is listed at 300ppm and soft is around 75ppm on my test strips.)

Whether your fish (if you plan to put fish in) prefer hard or soft water will depend whether you want to do anything to your GH, but there is certainly nothing wrong with it.

If you're planning to use CO2 injection, keep in mind that CO2 concentration is roughly proportional to pH for a given KH level ( http://atlas.csd.net/~cgadd/aqua/art_plant_co2chart.htm ). So if your default pH is 7.4 and after CO2 injection it's 7.0, at a KH of 9, you will have exponentially more CO2 in the water, than you would at KH of 5 for example. Again, not really anything wrong with this, just something to be aware of, especially if you opt to use a CO2 controller. I no longer use a CO2 controller myself, but on the one tank with a probe still, my tank hits 6.35 during the day and 7.4 overnight. My KH is around 4. You can see on the chart that if I had KH of 8, it would be double that CO2 concentration.

Most importantly for GH and KH is to keep it consistent. So if you're not doing anything to set it at that point, you're fine. If you are, then always do that. You may find that it slowly changes over time as I believe the Aquasoil influences it, but that's fine. As long as it's not an abrupt change. The values are a measure of dissolved minerals in the water and the fish acclimate to it. A sudden change means that the mineral concentration in the fluids of the fish's body are now different than that of the water. Which can cause fluids to be forced into or sucked out of the fish depending on which has the higher concentration. This is referred to as osmotic pressure.

For a long time I used RO water which has zero KH and GH without adding anything. Then I reconstituted it but somewhat randomly. I think I stressed my fish when I finally went to a consistent dosing scheme, but fortunately they pulled through and are happy now.

Michael


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