Rocks to Lower pH

[jonathan03]

My tap water is above 7.5 and I would like to lower the pH with rocks to about 7. Are there any rocks that will do this?

I know that there are additives you can put in your tank, but I think rocks would be better since they never run out. Its not important for the pH to be exact, I just need something that will lower it.

Right now my tank have two lava rocks, driftwood, and two mixed rocks (I forget the name). Heres a picture though:

http://enginecontrol.dyn.ee/Aquarium.jpg
http://enginecontrol.dyn.ee/Aquarium2.jpg

Hopefully none of the rocks I already have are rasing the pH. Are there any good rocks that will lower the pH? Thanks for the help.

 

[wynn]

AFAIK, there are no rocks that will lower PH. You can try driftwood though.

edit: just looked at the pictures, and see that you've already got driftwood. (doh!). Another idea is to use peat moss in your filter. It will turn your water a brownish color, but doesn't look all that bad.

Just curious, but why the need to lower the ph to 7? Most fish found in the stores will be just fine with a 7.5 ph, and would probably do better with the consistency rather than the fluctuations that is bound to happen from trying to adjust it.

 

[jonathan03]

I am growing live plants with Co2. At a pH of 7 or 6.8, there is the largest range of kH. Check out the table at the bottom of the page here:

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

The higher pH's have a much smaller kH range to be in the good range of Co2. I'm looking for a low maintenance tank with live plants. If there is rock or soemthing else to keep the pH low, that would be awesome.

 

[Karnaaj]

There are no rocks that will lower PH. Driftwood and/or peat are the best ways to go. I think you might be a little misinformed if you think that it will be low maintenance to try to keep your PH in such a narrow range. Sounds like a constant battle of tweaking if you ask me.

 

[happychem]

Well, first of all, I think that you've been misinformed about rocks, they do run out, everything does. It's just a matter of time and volume scales.

But more importantly you're misunderstanding the pH-KH-CO2 relationship. CO2 will lower your pH but will not have any effect on KH. Here's the key:
CO2 + H2O <-> H2CO3 (carbonic acid)
H2CO3 <-> H+ + HCO3- (acid and bicarbonate)
HCO3- <-> H+ + CO3-- (acid and carbonate)
The extent to which these reactions occur depends on pH (the amount of H+) and the amount of CO3 and HCO3.

KH is, to a very good approximation, HCO3- + 2xCO3--

CO2 reacts only sparingly with water, although the extent of that reaction is strongly governed by carbonate equilibrium, or KH and pH. If the water is already very rich in bicarbonate you'll need to dissolve more CO2 into your water to alter the pH (and carbonate equilibrium) than if you had very soft water. The former is a very desireable situation, it means that you can more safely and more stably dissolve CO2 into your water.

Those of us with soft water (<3dKH for reference) need to add crushed coral to our filters to prevent massive pH drops.

So you see, you don't really want to lower your pH and then add CO2. If your CO2 is dissolving well (or if you're adding a sufficient quantity), your pH will drop.

The higher pH's have a much smaller kH range to be in the good range of Co2.

You're reading the chart incorrectly, this may be the root of your concern over pH. Read KH from your tank, it's the "independant variable" (CO2 doesn't change KH) then use the chart to determine what pH you want to read and adjust your CO2 addition to reach that level. This is more easily achieved with pressurized setups where you can turn a needle valve and increase or decrease flow. With DIY it's a little more, um, artistic.

 

[johnnyxxl]

um unless you are looking at high tech planted tank, or dealing with a large load of plant life in your tank I do not see why you would need the high level of co2 that would cause a big ph swing or am I over lookin something. I think it may help us to know what you are really planning here ie more details like what plants how heavily planted and what fish that could help maybe figure out why you want to adjust the ph or actually why you need to is the more correct term as we know why now.

I should load my pic on the site its fairly grown in now low tech low light but very nice looking java fern and moss lots of plants all I do is 2 times a week water change and dose leafzone. no other chems other than prime to condition the water for chlorine and ammonia

 

[Harlock]

I am growing live plants with Co2. At a pH of 7 or 6.8, there is the largest range of kH. Check out the table at the bottom of the page here:

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

The higher pH's have a much smaller kH range to be in the good range of Co2. I'm looking for a low maintenance tank with live plants. If there is rock or soemthing else to keep the pH low, that would be awesome.

Look at the link of the tank in my sig. Planted, I dose Flourish Excel for Carbon, I have high pH and high KH and my gH was something like 420 last time I checked. Those plants were all small, 6 inches or less with only emergent growth when i bought them and they have been in that tank for a month and a half. So, you absolutely can grow plants well in high pH and KH.

Chemical additives cause serious yo-yoing in your pH, are expensive, and simply are ill-advised. All you have to do is use the right amount of CO2 or Flourish Excel for your pH and KH. It can be done, trust me. My tank is absolute proof that even an idiot can get it right.