alk and ac question

[kware]

My Ca. is always around 420 to 460 but my dkH is constantly around 5 to 6. ( a little on the low side ). Can I dose just alk and not ca? I don't need to raise Calcium so can I just use the alkalinity in my two part solution to raise alk to around 9 or 10. Or do I have to use both parts?

 

[sw500]

You can raise just the alk

 

[Jerm77]

I would also recommend that you watch your Magnesium levels as well. you will likely have precipitation of ALK and CAL if magnesium levels are too low.

http://reefkeeping.com/issues/2007-04/rhf/index.php

http://reefkeeping.com/issues/2006-06/rhf/index.php

 

[EvilMel]

Yeah. You can raise just the alkalinity portion, sure!

I agree with these guys that you need to watch your magnesium too.

You have to be careful of raising your alkalinity too much though because your calcium will plummet if your alk is too high.

 

[kware]

My Ca. is good 440 ppm, my Mg. is good to 1300 ppm. My main concern is the raise in PH. I dose in the early morning. Before I dose my PH is around 7.9 to 8.0 then after I dose the alk ,the PH goes up to 8.2. Then as the day goes on at the end of the light period the PH gets up to 8.4. Is my PH too high should I worry about this PH jump. Maybe dose every other day. What do you guys think?

 

[kware]

Thanks for the great links by the way jerm77

 

[Jerm77]

does your pH raise even when you dont dose? you may have excess co2 in your tank room / house. try circulating some fresh air. or if you have a refuge run the light cycle opposite of the tank. I think a .5 pH swing isn't so good.

you can also get alk mixtures that don't raise the pH, but lower it. but, I would first try to see if the pH swing is related to your dosing or not.

 

[Mariner]

Your pH is not too high, if anything it's probably a little lower than ideal on the low end of its daily cycle. Keeping your alk in the 7-11 dKH range will help minimize the pH swings.
HTH,
Mariner

 

[kware]

My PH raises throught the day even when I don't dose alk just not as much. Dosing the alk just makes it go up quicker and higher.

 

[Mariner]

<a href=showthread.php?s=&postid=15269293#post15269293 target=_blank>Originally posted</a> by kware
My PH raises throught the day even when I don't dose alk just not as much. Dosing the alk just makes it go up quicker and higher.

Rising pH during the day is to be expected...happens in every tank. 8.3+ is really ideal for a reef tank. What you want to do is keep it from swinging too low at night, and keeping your alk in the 7-11 dKH range is the biggest thing you can do to accomplish that. If you're worried about pH getting too high (which it is not right now) you might consider dosing Randy's Recipe 2, Part 2 alk formula found in this article and I'd highly recommend going over to the Reef Chemistry forum and perusing some of Randy Holmes Farley's reef chemistry articles
HTH,
Mariner

 

[tmz]

Ph rising during the day is primarily due to photosynthesis and is normal.8.6 and up is very high risk for precipitation of calcium carbonate;8.4 is good and no worry.

Alkalinity 7 to 11 dkh is the noted acceptable range. Corals have an easier time calcifying(precipitating calcium carbonate) at higher levels. It is quite common to dose extra alkalinity when using 2 part if calcification is occurring( corals and coraline growth for example) . Each 20ppm of calcium used in calcium carbonate precipitation wether it's biotic or abiotic uses up 1 meq/l(2.8dkh) of alkalinity .So in a growing tank the alkalinity will often require additional supplements of alkalinity to keep up.You can use the alkalinity portion of the two part or baking soda for this.

Stable acceptably high alkalinity gives the tank more buffering capacity and will help minimize ph swings. Gas exchange also plays a role. Photosynthesis can also help if a reverse photo period macroalgae refugium is used. Adequate surface agitation can help ensure good gas exchange and minimize CO2 builup if the house air is not high in CO2.

 

[kware]

Thanks for the good suggestions guys! Right now my refuguim lights are on all the time. I think I will swich them to a reverse photoperiod. Next I am going to look into Randys 2 part recipe. Right now at 12:20 pm 2 hours before my lights come on my PH is 8.12. My alk is around 7 or 8 right now and I am about to dose again. I will keep you posted.
Thanks again.

 

[tmz]

You are welcome, Good Luck.