Sodium bicarbonate vs sodium carbonate

[Myka]

Originally Posted by Reef Pilot

I am sure my pH varies from day to night time. What range do you consider good for SPS? Or conversely, what pH is bad for SPS?

It probably does. Most SPS tanks will start to suffer below 7.8 and above 8.4. Ideally, you want to be around 8.2-8.3, but as Chin says, don't chase the pH too much. Remember that pH is a result of several factors. It's like baking a cake...err...it's like a carburetor, you gotta get the mix right or it doesn't run properly. The "mix" primarily being CO2 and oxygen - though the source of CO2 (causing acidification, or lowering of pH) isn't always obvious.

[Reef Pilot]

Originally Posted by Myka

It probably does. Most SPS tanks will start to suffer below 7.8 and above 8.4. Ideally, you want to be around 8.2-8.3, but as Chin says, don't chase the pH too much.

Well, in that case I should maybe switch back to using carbonate. That is supposed to keep pH closer to 8.3. I still have a fair bit of bicarbonate left, though, so won't happen for a while yet. Meanwhile will do some pH testing at different times of the day, and see what mine is really at.

[Myka]

Sodium carbonate is also more concentrated because it isn't "hydrated" like bicarbonate. If you want to get real crazy you can dose carbonate at night and bicarbonate at day.

[Reef Pilot]

I did a couple of pH tests and results were pretty well as expected. In the afternoon, after lights have been on and bright for quite a while, the pH was 8.2. In the morning, before the lights have ramped up, the pH was 7.8. So it is within range, but not totally consistent. I guess the C02 buildup overnight is what drops it.

My test kit (API) is pretty old too, so results may not be totally accurate, although seemed to be what I expected.

Not sure what the results would be with the carbonate (vs the bicarb that I use now). I don't recall what my tests were (long time ago) when I was using sodium carbonate so have nothing to compare to.

Now the question is, should I switch to carbonate for my alk dosing?

[The Guy]

I have some sodium bicarbonate bulk 2-3lbs if anyone needs some.

[Duckhams]

Sodium Carbonate (Soda Ash) will significantly raise your PH for a short time after its's added and is more commonly used to 'maintain' alk/PH levels than Bicarbonate. Sodium Bicarbonate doesn't have such an impact on PH and is better for larger adjustments to your alk, which can be handy when setting up a new tank, QT etc. I'd go with the Soda Ash for daily dosing personally, however you may find the Bicarbonate goes a little further as it takes less to mix a gallon of solution. http://www.bigreefdepot.com/Bulk-Additives-s/149.htm