And Another Q about KH

[Skittyfish]

My kh is very low from the tap >2 d/kh. I have been adding crushed coral to my filter and am now up to 1 1/2 tablespoons. My kh is now 2.26 d/kh. My question is this...when I do a water change I always just use my python and take the water straight from the tap. This cause ph to drop and kh to drop also. How is this going to affect the water when I add CO2? Do I turn off the CO2 during and after water changes to allow the water to gas off? I am so confused.:confused: . I am trying to get my kh up to at least 3-4, and added another tablespoon of crushed coral after the water change today. But, this is also going to cause my pH to creep up more, it is already at 7.6, not too good for the fish I have, and I do know the CO2, when I get all the parts put together, will lower ph. I am rambling, any help will get lots of thanks.

[superjohnny]

Hmmm, let me try to answer this. I'm having a similar issue and here's what i've learned...

KH is the factor that determines the buffering capacity of your water. Adding CO2 will to water with a low KH will cause the PH to go down (because your water has a lower buffering capacity). So when you increase the KH your PH will have a lower tendency to increase or decrease. I think what you are asking is if you should add more crushed coral (more KH) because when you do water changes you take out some of the KH. My answer to this would be yes, add more coral.

I am really kind of stepping out of bounds here because I haven't really worked through this myself... in fact just two minutes ago I added sodium bicarbonate to my water to raise the KH. So we're kind of in the same boat you & me. :)

[djlen]

I'm guessing that from what you say you haven't started injecting CO2 yet. How long til you will be set up to start injecting?
My experience with crushed coral was that it didn't really affect the kH immediately, but took a short period of time. Sort of a build up affect. With that extra that you just talked about adding you should start to see an increase in both kH and pH shortly. You've already seen it come up some. If you can get it up to around 2.75 or 3.0 you should be ok, IMO, to start injecting slowly. Have you been using DIY CO2? If so, what were was your pH using that?
One thing for sure.....don't add any chemicals. It will come up naturally the way you're doing it.
Len

[Skittyfish]

No Djlen, no CO2 at all. I am just waiting on my needle valve so that I can see what type of connectors I am going to need.
I can't wait to get it started as my pH is rising slowly and My fish are soon not going to like it. Problem is when I add tap water it is causing the pH to lower, although I guess the kh is soon going to start countering that effect.
I have only been increasing the crushed coral every 3-4 days so far. I am trying to be sure that I am not adding too much too fast.
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I just test kh and pH. My kh is still >3 but it seems to be holding pH at 7.2-7.4. Had been rising to 7.6-7.8. But my lights have only been on about 30 minutes. I am sure it will rise as the day goes on due to the plants sucking out CO2.

[djlen]

Those numbers sound good. With a kH of 3, you will see a drop in pH when you start to add CO2. Why do you have a problem with the pH dropping? Do you have alkaline loving fish or something? And do I understand correctly that you are running your lights for 30 minutes a day?!? Why? I feel like I'm missing something here.
Len

[Skittyfish]

(lol) No, doofus. My timer turns my lights on at 10:00 am and i checked things at about 10:30 am. My ph always rises during the day and drops at night. The only reason I could find is that there are so many plants in the tank and they produce enought co2 at night to lower the ph and then during the day they use up the co2 and the ph raises slightly during the day so that by the time the lights go out around 7:00 pm the ph may have raised .2 -.4 more than it was when the lights came on. This was with a kh of about 1 d/kh or less though. Now I don't notice as big of a change.

[djlen]

Ok, now I understand what you were saying. LOL.
With the numbers you give, I don't see any problem with cranking up the CO2 when you are ready. I would let the tank stabilize now because I think you're going to see the kH come up some more(very gradually) and with it less fluctuations. When you add the CO2 it will again come down to a certain area and then level off. Start slowly when you add the CO2. Then you can adjust pH with the addition or subtraction of gas.
My water comes out of the tap at 7.4ph/3.2kH and with the addition of CO2 I bring it down to 6.5pH. I'm right were I want to be and the fish are fine, the plants are happy, life is good!
Len