alk buffers and pH

[jacksonpt]

I've noticed lately that my alk has been pretty low (~1.1) even though my ph has been fine (~8.2). I was concerned about how low my alk was, so I asked my LFS about ways to raise it without effecting ph. I was told that with typical alk buffers, ph will get to a point where it won't increase any more. Some of the new 'hot additive' (that what he called them ???) can push ph up past 9, but most typical, mainstream buffers won't push ph much past 8.4.
Well, I tried it. I tested my water before hand, ph-8.2 alk-1.1, everything else good. I used SeaBuffer from Aquarium Systems. I gave my tank 2 doses (1 dose for 2 consecutive days) like the directions said. I tested the water again... and sure enough, ph-8.2 alk-3.0, everything else still good. Not bad. I'll test again in a couple of days, make sure the levels are holding steady... but for now, I'm pretty happy.
Anyone else ever heard of or seen this kind of thing... like a ceiling on ph levels with typical alk buffers?
[ September 21, 2001: Message edited by: jacksonpt ]

 

[andymi]

I am not going to claim to know everything about this, but alkaline will essentially help keep your pH more stable. Also when the alkaline is a certain level your calcium supposedly dissolves better ( from what I understand). Keeping your alkaline higher at least about 2.5 meg/L you should be good to go and your pH swings should not be so bad. Just keep in mind that you should add your alk buffers in the morning before the lights come on in order to prevent large pH swings. If you have ever taken readings in the morning when lights are off, and at night when the lights have been on your pH will swing. Mine is typically 7.8-8.0 in the morning and 8.0 to 8.2 at night. I am in the same boat as you. My pH has always been fairly stable, coraline is growing and my alk was around 1.5 or so. I started adding Kent Marine pro dKH and have not had great success with it to raise my alkaline yet. Might have to try the stuff you are using
--Andy

 

[jamos6]

I use one of those buffers that maintains the ph and it has worked great. i use it every other week.

 

[keitho]

well, for what it's worth, here's what i know. alkalinity is a measure of the buffering capacity of your tank, i.e, resistance to change in pH. alkalinity is not only a measure of hydroxide ions (OH-), but also other buffering ions such as carbonate (CO3--), bicarbonate (HCO3-), bisulfate (HSO4-), borates, etc. anyway, chemically, these buffering agents can, depending on the pH, act as acids or bases. in this way, they can minimize pH swings in your tank. the pH IS different during the night and day because the biological inhabitants of the tank, especially those that photosynthesize, influence the chemical makeup of the water. during the day, the algae, corals, and plants use light to produce energy. a natural by-product of this process is oxygen, which acts to not only increase the dissolved oxygen in your tank, but also to limit the amount of carbon dioxide that can be dissolved in the water. at night without light, though, these organisms must respire, or use oxygen to break down stored food products. a by-product of this process is carbon dioxide. the C02 dissolves in the seawater to form carbonic acid, which can lower pH. i try to maintain my alkalinity around 4 meq/l, or 11.2 dKh. my alkalinity may be higher, but my test only goes to around 4 meq/l. anyway, the higher the alkalinity, the more insignificant the pH swings your tank will see. also, as for the solubility of calcium, it not only depends on what the pH of the solution is, but also on what calcium species is being discussed. for example, kalkwasser (CaOH) is much more soluble at pH 8.2 than calcium carbonate (CaCO3, the main constituent in invertebrate exoskeletons). anyway, calcium compounds are more soluble at a lower pH, to a point. AND, contrary to popular belief, kalkwasser does NOT contribute significantly to the alkalinity or buffering capacity of a tank as it is pure CaOH and contains NONE of the aforementioned buffering species. anyway, hope this helps and doesn't confuse...