Using sodium bicarb to increase alk

[molybdenumman]

I have low alk (~2.5 mEq/L) compared to my high levels of Ca (500 ppm) and Mg (~1600ppm). I would like to boost up my alkalinity. I have made the appropriate solution based on the alkalinty calculators.

Should I be doing water changes to get my Ca and Mg down or should i concentrate on my alk problems? If yes to alk, then do i add the solution (32g sodium bicarbonate / L) slowly over a few days or all at once?

Guidance would be appreciated.

Thanks

DanTheMan

[Chin_Lee]

I have low alk (~2.5 mEq/L) compared to my high levels of Ca (500 ppm) and Mg (~1600ppm). I would like to boost up my alkalinity. I have made the appropriate solution based on the alkalinty calculators.

Should I be doing water changes to get my Ca and Mg down or should i concentrate on my alk problems? If yes to alk, then do i add the solution (32g sodium bicarbonate / L) slowly over a few days or all at once?

Guidance would be appreciated.

Thanks

DanTheMan

Concentrate on the alk. As you increase alk, the ca and mg will decrease due to consumption by hard corals. At those high levels of ca and mg, do the increase slowly over a few days if you can or at least over a 24 hour period. But definitely not all at once or you will experience a drastic pH drop followed by an upswing.

The following link may be of assistance to you as well. Please note the concentration of sodium bicarbonate of these solutions are at about 74g/l or 149g/l (compared to your 32g/l).
http://www.advancedaquarist.com/issues/april2004/chem.htm

When I did use it, I used the 149g/l concentration (regardless what my pH was). I dripped the solution with an IV line at about 1-2 drops/sec for my system that has about 300g of water which is a very safe and extra conservative rate for the water volume that I have but it may be too fast for smaller systems ie a 5 gallon nano.
Hope that helps.
cwlee

[molybdenumman]

Thanks for the advice.

According to the site I read (same as your reference, different section), the 32g of sodium bicarbonate should raise the alk of my 90 gallon tank by 1mEq/L. Is that high enough (an increase from 2.5 mEq/L to 3.5)? Should I add more baking soda?

DanTheMan

[trilinearmipmap]

Go slow, there is no rush, it is easy to overshoot and if your alk goes to high you will have CaCO3 precipitating out as a snowstorm.

In addition, I would consider your pH and decide whether to use sodium bicarb or else baked sodium bicarb. If the pH is high (unlikely with low alk) then use sodium bicarb, if it is on the low side you might want to use baked sodium bicarb or a mixture of the two.

Just a couple days ago I tried to correct my low alk, overshot and now my alk is off the scale on my Salifert test kit, no ill effects on the tank but this is just a reminder to do small increments and test before each addition.