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PH vs Alkaline


Aug 3, 2007
Hello, I have read alot about the relationship of PH and Alkalinity. It seems that for the most part if your ph is low so is the alkalinity and vise versa. My proplem is that my ph is a little low at 7.8 and the Alk is high at 7.0meq. I read about using buffers or different things to lower the alkaline but they all seem to lower the ph as well. Is there something I can do to just lower the alkalinity level?? All my other readings are good: ammonia-0, nitrite-.2, nitrate-0, salinity 1.025, 60lbs live rock in a 60gal and about 73-75deg. thanks!!
Are you using RO/DI water? I will probably take a hit for this but ... I ALWAYS use a buffer for both my SW and my FW top offs. I like the Seachem Reef Buffer (Sodium Carbonate + unidentified ) buffer the best for dissolving (8.3 limited) and have been successfully using it for several years. I always mix my SW for at least 24 (usually more than 48) hours and let my FW set with the buffer overnight. I do not have problems with a stable PH unless I add unbuffered water. I also add calcium (separately), to the tanks to help minimize any negative effect of the buffer.

If you are not using RO/DI this may not be the best solution (you can over buffer). RO makes the water PH unstable and hence the need to influence it more than tap water. I have read that the nutrality of RO water SHOULD allow it to take on the PH of the tank but my experience has been otherwise.
Everyone should be using RO/DI, or at least RO water for their cephs!

A lot of people use buffers in top off water, and may need to add some to the mixed salt water (or to the water before mixing) - the different brands of salt mix make up saltwater with different pHs (and other readings). Kent is very low, Tropic Marin is usually 8.2and so forth.

Reef Central has published several studies about how salt water from varous salt mixes varies in its parameters.


Some people will use well water, other non-chlorinated ground water, premade SW or sea water instead of RO and that changes the aspect of the water so I wanted to qualify why I always use a buffer rather than using it as an adjusting measure. I guess I go a little overboard trying to be sure I qualify my posts :oops:

It may have something to do with my water but even using the "Reef" salt (now made by several of the manufacturers) that is designed for RO water I still have to buffer to get a high enough initial PH. I can use a little less to get the new water properly adjusted but I will see a drop in my tank PH after one or two water changes. Needless to say, I have gone back to the standard (and less expensive) mix and continue to control the PH by buffering. Bigpapa may want to test the unaltered PH of his initial water, again after adding the salt mix at 24 and 48 hours because at 7.8 it is more than "a little" low.
Yes, you're right, a few people use filtered sea water, but it's rare that well water will test pure enough to use (as least in the cases I've known and have been discussed on this site.)

Thanks marinebio guy, dwhatley, and nancy for the info. Couple things, I have tried water changes with tap and used the buffers. My most recent change I used distilled water that I premixed. I am in the process of researching ro/di converters for home use so I can just plumb that in and use for both. I think part of the problem is I tried that ph 8.2 and I read somewhere on here that using that could be bad as well. Anyway, today I just tested and now they moved a little closer together 7.9 and 6.5meq. I have heard about the seachem as well as b-ionic-- should I try one of these or just let it ride and see if it stabilizes on its own?? btw, my snails and hermits are all doing ok even still.
I would just let it ride. Most reefers don't really dose anything just to change pH. PH fluctuates through out the day and changes due to CO2 levels, so if you are dosing something to try to change it, it is easy to get caught up in chasing numbers. If you are testing make up water and its pH, you can often raise the pH by aerating the water. Actually that works for the aquarium too.

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