05-06-2009, 02:57 PM
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Originally Posted by Byron
I have only used dolomite, and when I had it in tanks as part of the regular substrate (for the livebearers and rift lake cichlid tanks) the pH of the tap water was very low (low 6's) and I never had fluctuations with 25% weekly water changes of more than a couple decimal points. The dolomite kept the pH steady according to the amount of dolomite. The tricky part is determining how much dolomite will do it. My tanks were high 7's and 8 constantly with pH 6 tap water. It is my understanding that dolomite also adds mineral to the water increasing the hardness. As I didn't have problems maintaining a steady pH, and the fish were behaving normally, I never bothered further. I'm not a chemist so I stand to be corrected on the hardness.
I have heard from others on this forum that coral achieves the same end. I've not used it myself. The problem with mineral water is the expense of buying it. Dolomite gravel is inexpensive and it doesn't take much. With soda, it is very temporary as you found out, so you are in that fluctuating pH scenario and with fish in the tank I would never do that. In the end it is easier on the fish if the pH is stable, even if not exactly at the preferred level. I assume the level you are aiming for is mid 6's (?).
Let me summarize so we're on the same page. The tap water is 7.0 and you started CO2 injection which will lower it, and in one night it went down to 5.0. The CO2 is off. But you've discovered that the ph is dropping without the CO2. Is this the tank "under progress" in your Aquarium photos? [Nice setup in my view, good balance with the plants--well done.] There are only 4 fish in it so that is not the cause of the dramatic pH drops. I wouldn't think there is sufficient wood to cause this, although I don't know what type it is (some might be more tannic, but the water looks clear not yellowish/brownish). I've not heard of gravel lowering pH, only the opposite if it contains calcium-based material. Did you put any nutrient material under or with the gravel for the plants, like flourite or eco-complete or similar? And what is the media in the filter...anything special?
Yes it's this tank (thanks for the nice words on it :) The wood is on the left is 'Zaire wood', and the other piece I have to say I don't know how it's called, but none of them release tanin (much to my disappointment!) I put little sticks under the gravel to feed the plants (those they sell in pet store, plastic sticks with holes in them) and it's said on the package that it doesn't affect water chemistry. I put liquid Flourish once a week and that's all. I've only got noodles and foam in the filter.
I've come to the conclusion that the Co2 didn't do much, it's probably purely coincidental since I started it after a big water change following the end of the cycling process, and since my water has low kh, it was probably the main factor, not the Co2
I've just bought some pieces of volcanic rock and limestone as a friend advised me that's how she got her kh up in ther cichlid tank. I've put a few small pieces to begin with-I'll see what happen! Right now the ph is between 6.0 and 6.5 and I am aiming for mid-6s so it's fine, not too much shift since yesterday. If that doesn't work, I will definitely look for dolomite or crushed coral- but since my cycling has just ended I can't switch substrate so it will have to go in the filter!
Thank you so much for your input!