Increasing Kalk to Raise Alk

[baldbean]

I measured my params last night and noticed my Alk was at 7dkH. I know this is in the "good" range, but I would like to get it between 8 and 9dkH. Lately I have also noticed that my pH swings between 8.05 and 8.45 (+/- .05). I dose kalk via my ATO setup (1.5 tsp for 5 gal reservoir) which adds about 12.5 mL of top off every 15 minutes. Below are my params:

NSW
Mag: 1365 ppm
Alk: 7 dkH
Ca: 400 ppm
pH: .4 daily swing

One trend I noticed is that during the hot months I had to up my top off amount so it would add about 25 mL every 15 minutes (2 x's the amount as now) and my dkH was between 8 and 9.You can check out my param history here .

So... because of the trend I saw during the hot months, my thinking was that adding more kalk to my ATO would raise my alk (and Ca), but I am worried that my pH will also be raised causing it to go over the safe zone. Would this be the case? Or would it be safe to add more kalk due to the fact that the alk being added will eventually tame the pH swings?

 

[dg3147]

I think if u raise your alk to 8 with baking soda (1 tsp disolved in 1 cup of RO/DI added to 100g will raise you about 0.5-1 dkh). Then u can "lock it in" with your kalk top off.

That pH swing seems fine since it is within range. I do not think it's the size of the ph swing that matters --so long as it swings within range. Alk stability is more important. Don't raise it too fast.

 

[jimmyj7090]

The kalk should be acting as a "balanced additive" meaning that it adds Ca and alk in correct porportions.

If you increase the kalk, you should see both Ca and Alk rise if anything.

If your Ca is good, then you should bring the alk up seperately, dg3147's suggestion is a good way to do that.

 

[baldbean]

I think if u raise your alk to 8 with baking soda (1 tsp disolved in 1 cup of RO/DI added to 100g will raise you about 0.5-1 dkh). Then u can "lock it in" with your kalk top off.

That pH swing seems fine since it is within range. I do not think it's the size of the ph swing that matters --so long as it swings within range. Alk stability is more important. Don't raise it too fast.

Locking it in does sound like a good idea. Thanks for the formula. A friend of mine just did this and it seems to have worked well.

The kalk should be acting as a "balanced additive" meaning that it adds Ca and alk in correct porportions.

If you increase the kalk, you should see both Ca and Alk rise if anything.

If your Ca is good, then you should bring the alk up seperately, dg3147's suggestion is a good way to do that.

That was my thought too. Because kalk behaves that way I didn't think it would be bad to increase the amount. I'm just a little paranoid about adding too much at once.

Thanks for the replies.

 

[bertoni]

This calculator will help with doses:

http://reef.diesyst.com/chemcalc/chemcalc.html

It takes about 2.5 tsp of baking soda to raise 100g of water by 1 dKH.

 

[baldbean]

Thanks bertoni.

 

[blanden.adam]

You certainly could up the amount of Kalk you are using in your ATO, but you are approaching the upper limit of solubility for kalkwasser in water at room temperature (~2 tsp/gal), at least without the addition of acid (e.g. vinegar). I wouldn't worry all that much about how it impacts the pH of the aquarium as long as you are not adding it at such a rate as to cause pH spikes and your aquarium is well aerated. Remember, although you are adding base to the aquarium in the form of hydroxide, that hydroxide reacts with carbon dioxide to form bicarbonate (neutralizes an acid, raises the pH), which then via Le Chatelier's principle causes more CO2 from the air to dissolve into your aquarium water (add's an acid, lowers the pH), so your pH shouldn't really increase all that much, particularly if you are mixing your kalkwasser with vinegar beforehand.

However, as other members have already stated, you should NOT increase your kalkwasser to try and increase your alkalinity, but rather use some form of calcium salt (like calcium chloride) and a bicarbonate additive (like baking soda) to set your numbers where you want them, and then titrate your kalkwasser to keep your level of calcium and alkalinity constant.

As a second note, when monitoring your calcium and alkalinity levels, remember that alkalinity is much more sensitive than your calcium to the amount of additive you are using, and will both drop and rise faster than your calcium level, oftentimes making it look like you are using more alkalinity than calcium, when in fact our test kits simply aren't sensitive enough to pick up a drop in calcium corresponding to a drop in alkalinity. So, when titrating your kalkwasser, use the alkalinity as your guide.

 

[baldbean]

You certainly could up the amount of Kalk you are using in your ATO, but you are approaching the upper limit of solubility for kalkwasser in water at room temperature (~2 tsp/gal), at least without the addition of acid (e.g. vinegar). I wouldn't worry all that much about how it impacts the pH of the aquarium as long as you are not adding it at such a rate as to cause pH spikes and your aquarium is well aerated. Remember, although you are adding base to the aquarium in the form of hydroxide, that hydroxide reacts with carbon dioxide to form bicarbonate (neutralizes an acid, raises the pH), which then via Le Chatelier's principle causes more CO2 from the air to dissolve into your aquarium water (add's an acid, lowers the pH), so your pH shouldn't really increase all that much, particularly if you are mixing your kalkwasser with vinegar beforehand.

However, as other members have already stated, you should NOT increase your kalkwasser to try and increase your alkalinity, but rather use some form of calcium salt (like calcium chloride) and a bicarbonate additive (like baking soda) to set your numbers where you want them, and then titrate your kalkwasser to keep your level of calcium and alkalinity constant.

As a second note, when monitoring your calcium and alkalinity levels, remember that alkalinity is much more sensitive than your calcium to the amount of additive you are using, and will both drop and rise faster than your calcium level, oftentimes making it look like you are using more alkalinity than calcium, when in fact our test kits simply aren't sensitive enough to pick up a drop in calcium corresponding to a drop in alkalinity. So, when titrating your kalkwasser, use the alkalinity as your guide.

Thank you.

Agreed baking soda does seem to the way to do it. My thinking was since I am at 0.3 tsp/gal (1.5 tsp per 5 gallons) that going up to 0.5 tsp/gal (2.5 tsp) and get a 2 for one.

 

[blanden.adam]

Color me red, missed the 1.5 tsp per 5 gallons. And exactly, if you are losing alkalinity between water changes, just slowly titrate your kalkwasser up. Definitely keep an eye on pH, but like I said before I wouldn't worry about it too much.

 

[bertoni]

Oops, I missed that, too.

 

[allsps40]

I would dose and do dose kalk. Your alk being at 7 is on the low side as is the Ca. Kalk in your ATO will slowly increase and maintain alk and ca levels a good idea for your situation.