cheap safe PH down?

[KLee79]

what about baking yeast in a 2 ltr bottle? thats pretty cheap..try diffusing the co2 and this will naturally bring your ph down a bit.

 

[brianp]

If there are no negative effects of using it, this might be the best idea yet. Have you tried it yourself? Are there any side effects that you know of?

I have not used vinegar for this purpose because I don't need to drop my pH. Acetic acid is a weaker acid than, say hydrochloric acid or sulfuric acid. This means that you may only achieve 90-95% dissociation initially, whereas HCl will completely dissociate. So, after you add vinegar initially, you will have the following in solution: acetic acid (undissociated), acetate and H+. Then, as the bacteria consume the acetate, there will be further dissociation of the remaining acetic acid to liberate more H+. You may never notice this effect, but if observed, it will manifest itself as a slow, slight downwward drift in pH...probably over the next couple of days. I really don't expect this effect to be noticeable, but if it is, it simply means that the pH will slowly drop a bit lower that what you first recorded when you initially added the vinegar. Bascially you need to take a gallon of aquarium water and gradually add known amounts of vinegar until you reach the desired pH. This will tell you the amount of vinegar per gallon required. Multiply this by the total number of gallons to determine the volume of vinegar required for the entire tank. You can add maybe 80% of this amount and see where the pH is. After lowering your tank to the desired pH, continue to monitor over the next few days to see how the system is responding. If you undershoot the pH, add small amounts of baking soda to increase the pH. The bacteria might also consume the acetic acid directly, so the pH may, in fact, be quite stable once you have added the requisite amount of vinegar. You won't know for sure and this is why you will have to add what you believe is a reasonable amount and then monitor changes in the pH for several days thereafter.

Biological systems are loaded with acetate and I can't imagine any deleterious effect from adding vinegar.

 

[spiff]

I have not used vinegar for this purpose because I don't need to drop my pH. Acetic acid is a weaker acid than, say hydrochloric acid or sulfuric acid. This means that you may only achieve 90-95% dissociation initially, whereas HCl will completely dissociate. So, after you add vinegar initially, you will have the following in solution: acetic acid (undissociated), acetate and H+. Then, as the bacteria consume the acetate, there will be further dissociation of the remaining acetic acid to liberate more H+. You may never notice this effect, but if observed, it will manifest itself as a slow, slight downwward drift in pH...probably over the next couple of days. I really don't expect this effect to be noticeable, but if it is, it simply means that the pH will slowly drop a bit lower that what you first recorded when you initially added the vinegar. Bascially you need to take a gallon of aquarium water and gradually add known amounts of vinegar until you reach the desired pH. This will tell you the amount of vinegar per gallon required. Multiply this by the total number of gallons to determine the volume of vinegar required for the entire tank. You can add maybe 80% of this amount and see where the pH is. After lowering your tank to the desired pH, continue to monitor over the next few days to see how the system is responding. If you undershoot the pH, add small amounts of baking soda to increase the pH. The bacteria might also consume the acetic acid directly, so the pH may, in fact, be quite stable once you have added the requisite amount of vinegar. You won't know for sure and this is why you will have to add what you believe is a reasonable amount and then monitor changes in the pH for several days thereafter.

Biological systems are loaded with acetate and I can't imagine any deleterious effect from adding vinegar.

Interesting data. I guess that's why its not commonly used then. Basically, it would take a LOT of vinegar to do what very little acid could. So its sort of a trade off.

Thanks for the feedback. I think I'll stick with the General Hydroponics PH down then. I was sitting on several gallons already. But I also wanted to see what the current available price is, I can get it for $25 bucks a gallon.

I do think that other more pure forms of sulfuric acid would work too.. like the Liquid Fire drain cleaner. But there are issues with safe handling when dealing with acid in such a pure form. For one thing, the stuff will corrode metals nearby even through a closed bottle if it sits long enough. And the stuff emits fumes which are toxic. Then there is the obvious issues of actually using it. Its more reactive and you wouldn't want to get any on you. This GH PH down is pretty mild in comparison.