[fishymatty]

does the GH of water change if you don't change it? For instance, my tap is about 80ppm, after 4-5 days is the tanks water still going to be the same? I don't really check it because it is niether too hard or too soft to worry about it.
Next, my ph is about 7.2 out of the tap with a kh of about 30ppm(1.75°). In one of my tanks this ph is good but with the addition of co2 the ph fluctuated quite drastically. Now my question is, does the kh effect the fish. say I raise the kh but the ph stays the same how does this effect the fish? I have the kent kh, and I put too much in one time and the ph only went up .2 but the kh was 240ppm. not at once but over the course of a few days.
•gh does it change over time in the tank

•kh what is the difference to the fish if the ph is 7.2 at 30ppm or 7.2 at 240ppm(hypothetically)

 

[Rex Grigg]

KH and GH in a planted aquarium will slowly drop over time.

If the KH is 30 ppm at a pH of 7.2 then you would have CO2 levels of 3 ppm or basically no CO2 injection.

If the KH is 240 ppm and the pH is 7.2 then you would have CO2 levels of 25 ppm.

CO2 will cause the pH to drop.

pH changes caused by CO2 do no harm to fish.

Raising KH too quickly can harm fish.

Baking soda is a much cheaper way to raise kH.

 

[fishymatty]

gh drop over time, but doing 20% water change every couple days should do the trick.
What is KH(carbonate hardness) that makes it harmful for fish when raised or lowered in excess or to quickly?
How much is too much to adjust kh at once?

 

[Rex Grigg]

Raising either the GH or KH too quickly can harm the fish. It upsets the Osmotic balance in their bodies.

I would not go more than 0.5 degrees every 12 hours.

 

[Hypancistrus]

The blanket statement "GH will drop over time" is NOT true for everyone. Each tank and situation differ. In some situations, GH will increase over time. It depends on the substrate, what you dose, how often you dose, and if you are replacing evaporated water with tap water.

For example, if you don't have anything in the tank that has an effect on lowering GH (such as peat), and you top off the tank with tap water over a two week period, and that tap water has some level of calcium in it, GH will definitely rise over that two week period. (How much would depend on how much water is evaporating and being replaced, and the level of GH in the tap water.)

 

[Rex Grigg]

That's true. But I did not want to complicate it. All things being equal GH will go down if there is nothing added to the tank that will raise it.

 

[fishymatty]

I understand all that about gh, but I'm not too worried about that, I do water changes every couple of days so it stays consistent. But my real question is about the kh, I try to keep it consistent but some times I raise it too much,this all stems from the fact that the kh out of my tap is under 30ppm and I like to keep my co2 as high as possible to try to combat my algae problem so I get concerned that the ph will drop and harm my fish. But rex said that ph drop due to co2 injection will not effect fish, if this is true than i wan't even bother adjusting my tap.

 

[Naja002]

You have Great Water. Honestly: You are just beating yourself up worrying about it and trying to adjust it. Just leave it alone: You are in a much better boat than most of us.....:thumbsup:

Take a read through these threads:

Low or no KH and low PH without a "crash"??

Low KH and pH crash

HTH