Alkalinity Low

[gyannakoul]

I am looking for some help with an alkalinity issue. My alkalinity (without any additives) is about 7.0. I use Reef Crystals for salt and the water that I use for water changes has a pH of about 6.0. My calcium levels are at about 490 and my Magnesium at over 1500 ppm.

My question is this, should I be using only buffer (i.e. CaCo3) without Calcium or should I be using the same amount of Calcium as Carbonate (as in two part). I've read or seen somewhere that it is not appropriate to add just buffer without Calcium as in 2 part. This does not make sense to me as I already have high Calcium levels and it would seem that adding only buffer for now to bring up the alkalinity to about 8.2 or so for my corals would be more appropriate. Does anyone have any knowledge of this? It would be greatly appreciated.

 

[tmz]

I'd just add the baking soda(NaHCO3) or soda ash (NaCO3) for a one time adjustment to alkainity and then adopt a balanced Caclium chloride /carbonate) two part dosing scheme. The reef calculator in teh sticky at the top of this forum can help. Try to keep any alk adjustment under 1dkh per day.

Going froward,if your tank is receiving more calcium than it's using in making calcium carbonate ,from high calcium in your salt mix for example ,you can tweak the alk an calcium proportions in two part dosing to reach a constant level in your tank for both of them.

 

[gyannakoul]

you mean tweak the levels of calcium and alk added but they do not have to be the same amounts of calcium and alk......right? For example, I can add 1 ml of calcium and 10 ml of alk?

 

[outssider]

if your alk is 7 and calcium is 490...just add alk for now till you get it where you want it. The calcium will drop slowly as you raise the alk....soon you'll be in an acceptable range for both...then dose each one (alk and calcium)...you should end up dosing close to the same amount of both but dose what's necessary.

 

[bertoni]

I agree with dosing just the alkalinity for now. The calcium level likely will drop, although water changes might keep it very high. Every tank has a different consumption rate for calcium carbonate formation, so I'd just measure for a while and get a good trend line. Calcium changes very slowly compared to alkalinity, so measuring once a week might be more than enough for a while. The ratio should be about 2.8 dKH per 20 ppm of calcium consumed.

 

[jonwright]

I've the same thing (low alk, high CA) using reef crystals. I does alk in my ATO only for a while, once CA came down I went over to kalk. The water changes are putting the CA back so I raise up the alk in my fresh sea water before doing my weekly water change.

While alk will go down I understand from RFH's articles that your critters should use the two chemicals in a balanced fashion. Right?

Now that I'm using Kalk the Alk is staying where it needs to be and the CA is right - so far.

Is there ever a case where outside of balanced usage that a tank will consume MORE alk in proportion to CA?

 

[tmz]

It's not a perfectly balanced consumption but very close; incorporation of other elements in the skeletal mass such as phosphate and magnesium effect the carbonate to calcium ratio of 50ppm to 20ppm but not by very much.
Some biological activity using alk and not calcium might also occur with a sulfur denitrator as one example.

Most likely the salt mix is contributing disproportionate amounts of calcium and carbonate alkalintiy;or the water source might be high in calcium; or the two part mix may be off.

 

[bertoni]

I think Tom has given some good examples of increased alkalinity consumption, outside of the 2.8 dKH to 20 ppm calcium rule. The difference generally is small, though.

 

[tmz]

you mean tweak the levels of calcium and alk added but they do not have to be the same amounts of calcium and alk......right? For example, I can add 1 ml of calcium and 10 ml of alk?

One time adjustments or tweaks with just the carbonate/alk part or calcium are doable with care not to use too much.

Usually, dosing a balanced amount of two part works very well and is recommended. FWIW, I use kalk which provides a balanced proportion of calcium and carbonate alkalinity just like a balanced dose of two part does.

Sometimes, high calcium or alk salt mix levels adds them in different proportions (some of them add as much as 580ppm calcium with 8dkh alk; some are high in alk ). Continuing to use such a salt salt mix is ok ; the dosed proportions of alk /caclium via two part can be adjusted to account for the inputs from the salt mix.

For example if you do water changes with a salt mix holding high calcium ,you can account for that by reducing the proportion of calcium you are dosing when using two part.

 

[Reduck]

Thank you all.
I just did a search on low alk and this thread has been very very helpful!
I'm using Red Sea Coral Pro and it tends to be higher in everything, but my alk tests considerably lower a couple of days after a wc. You have confirmed I am taking the correct steps. I hit it with baking soda per calculator to get it back up, then adjusting my 2 part Cal, down to 1/4 of Alk. I'll test in a couple of days to see where it trends.
thanks again...

 

[bertoni]

You're welcome. Good luck!

 

[gyannakoul]

Low Alk levels

Low Alk levels

O.K. guys. Thanks for your help in answering my initial question. I figured as much regarding dosing Alk first until Ca went down but was not absolutely certain so wanted to check.

 

[bertoni]

You're welcome.