Does ph and kh really matter?

[FishyMatty]

I have Three tanks, all of which are co2 injected. The water right out of the tap is ph7.2 kh10-20ppm.
2-45gal, 1- 20gal.
20gal- I add a little baking soda to raise kh.
One 45g has my discus in it along with many tetras, ottos and SAE's. The other one is newly emptied, Heavily planted and cycled ready for the discus to be moved in.
In both the 45g I use seachem acid buffer and baking soda to lower ph to 6.6 and raise kh to 80ppm.

•Question•
If I acclimate my fish to the tap water parameters(ph7.2/kh10-20ppm) What would happen to the ph with the injection of co2?
If the ph drops how much will it/can it drop?
Is that bad for the fish?
How should I go about eliminating the use of acid buffers and baking soda?

[Rex Grigg]

Whenever you inject CO2 (assuming a decent diffusion type) you will drop the pH. However the pH drop caused by CO2 doesn't harm the fish.

One would normally shoot for a 1° drop in pH to get to 30 ppm of CO2. So your goal with tap water would be 6.2°.

To reset your tanks you need to do 50% water changes every day for 4-5 days. That will basically get you to your tap water settings.

[nickmcmechan]

http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm

[FishyMatty]

Rex, thank you and nick that was the information I have been looking for in writing all along.
I guess the only thing I am a little skeptical about is the ph swing. From the very beginning of my fish keeping I read that the worst thing for fish next to ammonia and nitrites is any significant change in ph. Now I'm not saying I don't believe you but if you could explain it to me I would feel better about it. Also, I have never aged my water. I know this is bad practice but my life just doesn't allow for things like that. So with a tap ph of 7.2 and kh of 10-20ppm will I be ok doing the water changes recommended by rex and adding co2. I wish I was home now with the new info I have so I could age some water and find out what the truth about my water is.

[Rex Grigg]

Who ages their water? That's so old school it's not funny. I drain. Treat. Fill.

14. Since CO2 will cause the pH to go down will this change in pH hurt my fish?

No. Normally in the wild pH changes are caused by changes in the kH (carbonate hardness) and TDS (Total Dissolved Solids) in the water. These changes can cause osmotic shock to the fish if they are large enough. Most all fish can handle a bigger pH change due to hardness than many people think. In many places where our fish come from a rainstorm can cause a huge change in pH. When CO2 lowers the pH it doesn't affect the kH or TDS. So the osmotic balance is not upset.

From www.theplantedtankFAQ.com

[FishyMatty]

I figured as much. But in that website it says the ph and kh of tap water will change after its been sitting for a while. How will this info effect me?
rex can you read my last response and see if you can answer the questions I had. You have been a huge help so far.

[nickmcmechan]

I wouldn't get too hung up on aging water as long as its conditioned you'll be fine.

I can speak from experience and say that CO2 related pH swings do not stress fish.

How often are you home normally, maybe we can helpyou workout a practical maintenance plan?

All the advice I've read on this forum says do not use buffers, so what exactly is the reason you are trying to control your pH and kH so much?

[Rex Grigg]

The pH of water will change. This is due to dissolved gases leaving the water. But again. pH changes caused by dissolved gases mean nothing.

Read my response. Think about normal pH changes in water and how they go hand in hand with changes in hardness and TDS.

Now think about pH changes caused by CO2. No change in hardness and no change in TDS.

It's the changes in hardness and TDS that stress fish. Not the pH.

You have to separate cause and effect.

In nature the cause of pH changes is changes in the hardness and TDS. The effect of changes in TDS and hardness is changes in the pH. (I know I most likely mangled that one). But if you can change the pH without changing the hardness and TDS then you remove the problem.

[FishyMatty]

to answer nicks question. I am new to co2. I have had it about 3months and I have discus so I wanted to try to keep them happy. Most of everything I read up till now was the opposite of what I read on that site you gave me. But I get it now and I am excited that my water changes and all over tank care will be so much less work. As far as how often I'm home. I usually get home every night mon.-fri. and home at least one day on the weekend but I had to drive out to chicago for a wedding. So I will be home on mon.
Thanks again nick and rex. You have both made life so much easier.