Dosing Alk with baking soda

[Cymonous]

My Alk was low at about 6.4 dkh. I heard I can get it raised by dosing with a mixture of baking soda and some RO or RODI water. I followed a calculator that said to use half a tsp of baking soda dissolved in RODI. I added the baking soda to a half gallon jug. I use this as my top-off, but my tank evaporates very little water. It is the 14g biocube that has the lid and small holes in the back. So, I only have to top-off about a cup and 1/2 a day. I know I am suppose to dose this mixture slowly, but is this going a little too slow? I want to get the dkh to about 8.5. Should I make a new mix with less water?

[downbeach]

Add 1 1/4 cups of A&H baking soda to 1 gal. RO/DI water(I use a hand blender to mix). Fill in the blanks, using this calculator (http://reef.diesyst.com/flashcalc/flashcalc.html), and Randy's recipe 2 in the alkalinity section to determine how much to add. Don't add more than 1 dKH per day.

[disc1]

You can make that with a lot less water. But keep in mind you don't want to raise alkalinity by more than 0.5 to 1.0 dkH per day so you should split that much up over three or four days.

[Cymonous]

That was the calculator I was using. So, it does sound like I was dosing very little a day then. And for what I can tell, I should be able to use about 1/4 tsp of baking soda mixed with a little RODI a day then.

[Daimyo68]

Honestly, in a BioCube of 14g, you should be able to keep up with Alk (and other levels), if your doing a weekly 2g water changes. I would have your water tested again at the LFS or a different LFS to confirm your low alk readings. What was the pH, and other readings?

If your going to be dosing Alkalinity, you need to keep an eye on your other readings as well, to make sure that the balances stay within range.


If you want to try manually dosing Alkalinity, then you need to do the following:
If using Baking Soda, then as mentioned, mix 1-1/4 cups of baking soda with 1 gal of RO/DI water. This will give you 1 gal of Alkalinity additive.

For your tank (and it's numbers) you will need roughly 41-42ml of Alkalinity to go from 6.5 to 8.5dKh

Start off by adding a 1/2 cap full (roughly 2.5ml) of the Alkalinity in the morning before you go to work, and check you level later that day when you get home from work/school.

As an example: your at 6.4dKh, you add a 1/2 cap full in the morning. You test that night and now your at 7.0dKh. Do this again then 2nd day, adding 2.5ml in the morning, and test that night. If you see that you Alk is rising, then keep this up for the next few days until you reach 8.5dKh. (NOTE: As mentioned, you do not want more than 1.0dKh change within 24hrs. If you see that much of a change, cut back to a 1/4 cap full)

On the day that you test and your alk is at 8.5dKh, stop adding it. Now, test your water the next couple of days in a row, and write down what it drops to each day. This is how you will figure out your daily usage. Example:
Day 1 - 8.5dKh
Day 2 - 7.8dKh
Day 3 - 7.2dKh

You can see that your system use roughly 0.6dKh per day, which is roughly 12ml per day. At this point, bring your alk back up to 8.5, and now start adding ~12ml per day. Add a cap full in the morning, and a cap full before going to bed (after the lights go out in the tank) This will help avoid Alk/pH spikes. Adding it twice a day should keep your level within acceptable ranges.

[Cymonous]

I did have my water tested last week by my LFS, but all they had were test strips. I don't remember the exact reading, but I do know the Alk was low. I just got this Red Sea Pro kit last week.

You are probably right that I should be able to maintain the levels with water changes in such a small tank. I started about a month ago where I make 2gallon saltwater(IO Reef Crystals) in a bucket with a small PH and heater and it goes for about a week before I do my next change. I have heard the precip may cause Alk to decrease though. I have stopped making this long prepared water and I am going to start doing a max of 24hr prep instead.

[Daimyo68]

24hr mix time is more than enough. This usually works for most people because you make the water one night, and then do the WC the next night.

Definitely test the levels with your new test kit before trying to adjust anything.

[natron]

For recipe 2 are you baking the baking soda like recipe 1?

[downbeach]

For recipe 2 are you baking the baking soda like recipe 1?
No, that recipe calls for straight baking soda.

[dkeller_nc]

You are probably right that I should be able to maintain the levels with water changes in such a small tank. I started about a month ago where I make 2gallon saltwater(IO Reef Crystals) in a bucket with a small PH and heater and it goes for about a week before I do my next change. I have heard the precip may cause Alk to decrease though. I have stopped making this long prepared water and I am going to start doing a max of 24hr prep instead.

Personally speaking, I don't use newly-made seawater until it has been circulating at tank temp for at least 48 hours. However, I have a set-up that allows me to make 45 gallons at a time, and the container has a cover that prevents a good deal of evaporation.

The issue I'd see with what you've described is that at a 2 gallon total volume, there would be a good deal of evaporation over a week's time. If you were to check it daily and keep adding RODI water to keep the specific gravity at 1.025 or so, no problem. But if the specific gravity gets into the 1.035 range or so, you could definitely be getting precipitation of calcium carbonate and magnesium carbonate before you use the water.

One final thought - an alkalinity of 6.5 dKH isn't a big deal. Yes, it's a little low, but it's not going to cause a major problem with soft corals and LPS. As others have noted on the thread, the danger is more with rapidly adjusting the alkalinity to what is perceived to be "good".