Acid 'buffer'. Nice work altum. It was an interesting puzzle while it lasted.
NetMax On Feb 2, 9:59 pm, Altum <[email protected]> wrote: > On Feb 2, 11:51 am, NitroCarbon <[email protected]> wrote: > > > On 02/02/2011 01:28 PM, NitroCarbon wrote: > > > > No no. Water off the RO unit has KH of zero. It only gets up to 6 when > > > I have buffered it. After buffering I have a KH of 6 and a pH of 6.8 to > > > 7.0. > > > BTW, unbuffered water fresh out of the RO unit has a pH of 6.4 to 6.8. > > Gah. The problem is the Acid Buffer. I've never used it in a heavily > planted tank because I always add only carbonate and CO2. I was using > Acid Buffer to lower pH in with my "liquid rock" tap water and now I > see why it worked so nicely. > > From Seachem's website "As Acid Buffer™ lowers pH it converts > carbonate alkalinity (KH) into available CO2. It may also be used to > safely lower pH in marine water." > > From the MSDS, Acid Buffer is apparently bisulfate salts, probably > sodium and potassium. Sulfate has a very low pKa so it's acting more > as an acid than as a buffer. "Buffer" is a complete misnomer. > > So, what's happening is that you add Alkaline Buffer/Acid Buffer. You > get the pH Seachem has determined in your RO water and the water has a > fair amount of CO2. You add the water to the tank, plants use up the > CO2, the acid buffer starts eating at the KH. Sulfate doesn't buffer > effectively at aquarium pH ranges so what's left of the carbonate > system takes over and pH climbs as plants happily strip all the CO2 > from the water. You end up at the natural, high pH for water with > very little buffering capacity and very low CO2. > > Simple solution: Stop using the Acid Buffer. After digging about on > the Seachem site, I'm sorry I even suggested it for RO water. Ugh. > You're just chasing your tail, lowering pH by releasing CO2 and > breaking the carbonate buffering system. I thought that product was > something sensible like ascorbate, not bisulfate. > > Until you get CO2, set KH to 2-3 with Seachem alkaline buffer, put GH > where you want it. Keep your tank well aerated to keep the CO2 > concentration from bouncing from photosynthesis. It will probably > still go up by evening if the tank is brightly lit, but there isn't > much to do for that. Your fish should be fine if the water is clean > and soft, even with the pH a little high until you get CO2. Do keep > an eye on KH to be sure your plants don't "eat" the carbonates too > fast between water changes. You may have to add a bit of alkaline > buffer every week. For non-CO2 tanks, many discus keepers use > blackwater extract or peat to soften and condition the water and lower > the pH slightly. > > --Altum
