Chasing parameters

[jetlink82]

I have had my 90G up and running for over a year now and recently started adding coral to the tank in hopes of turning it into a mixed reef. My KH has been low, around 6.7-7.0. I just started dosing "REEF alkalinity" to bump up my alkalinity to at least 9 or so (slowly). After 3 days of dosing my KH has reached roughly 8.3 but seems to keep dropping every day. My calcium is at 430-440, salinity is 1.025, magnesium is at around 1260 (which I believe is low?). All tests are done using Salifert kits and a refractometer.

I am thinking about going to the LFS to pick up a bottle of magnesium to try to get it up to 1350ish? I know that magnesium should be at least 1300 for calcium and Alk to be stable...or so I have been told at least. I have been testing my water at least once a day...maybe I should just leave it and not worry about it so much. I am doing water changes weekly (10-15%). My corals are doing very well.

 

[xyzpdq0121]

I have said it before but I would read Randy Holmes Farley's articles on the subject. If you are confused from there THEN ask questions.

Is reef alkalinity bicarbonate or carbonate? I also would save your money on commercial magnesium supplements and do a DiY supplement.

 

[jennm]

What salt mix are you using?

How does your livestock LOOK? Sometimes looking will tell you a lot.

What test kits are you using? They aren't all created equal.

It's good to test, but sometimes folks get too hung up chasing numbers when things are fine. Depending on what kits you're using you may want a second opinion.

The alk seems low but CA, MG and SG are within acceptable range, IMO. MG I always aim for 1250-1350.

What's your pH at? I don't see it listed.

Jenn

 

[jetlink82]

PH is at 8.0, always there and I don't worry about PH much, I am using Salifert test kits. All my fish are perfect, corals are doing great.

I did a water change today and tested the water tonight. MG is at 1290, I am not going to worry about it, good enough and everything is doing great.

 

[tbub1221]

Jetlink82;940708 wrote: PH is at 8.0, always there and I don't worry about PH much, I am using Salifert test kits. All my fish are perfect, corals are doing great.

I did a water change today and tested the water tonight. MG is at 1290, I am not going to worry about it, good enough and everything is doing great.

Do you use a ph buffer ? that can drive down your alk and I know many ppl running fowlr tanks use buffers.
I ask because you said its stable but its been my experience that ph is stable when alk is stable and if your alk has been that low it doesn't make a lot of since that ph would not swing some .
But it that were the case would the livestock not reflect it , so maybe your test kit is expired or something.

 

[jennm]

What salt are you using?

 

[jetlink82]

Tbub1221;940737 wrote: Do you use a ph buffer ? that can drive down your alk and I know many ppl running fowlr tanks use buffers.
I ask because you said its stable but its been my experience that ph is stable when alk is stable and if your alk has been that low it doesn't make a lot of since that ph would not swing some .
But it that were the case would the livestock not reflect it , so maybe your test kit is expired or something.

Not using a PH buffer. Every time I test, the PH shows up as 8.0. I am using brand new Salifert kits for PH and Alk. I think I have the water where it needs to be and stable now that I am using the alk buffer.

 

[xyzpdq0121]

Tbub1221;940737 wrote: Do you use a ph buffer ? that can drive down your alk

Just wondering what PH <u>buffer</u> lowers your Alk? Are you talking total Alk or specific Alk?!? Either way, you would need a strong acid for that (Sulfuric, Phosphoric, Hydrochloric, or any acid with a pKa that is pretty low. Normal acids like carbonic acid will lower PH but have no effect on Alk.) So I am wondering, what buffer (Basic [as in acid/base] by definition), has the pKa of Hydrochloric acid?!? Not to sound rude, but there just is not one by definition. All commercial "buffers" are a either straight bicarbonate, carbonate, or a mixture of the two and borate, silicate, magnesium monohydroxylate, hydroxide, or even phosphate. (I have never seen a commercial Ammonium [NH4-] or ionic Hydrogen Sulfied [HS-] but they would also contribute to total alk and <u>could</u> be put into a commercial mixture.) All these compounds would have an effect of your total alk and SOME effect on your PH. Some more than others but no "buffer" is going to "drive down your alk". Heck it is not going to "drive down" your PH for that matter!

Back to the subject at hand, please note that the original poster is relying on titration PH tests. By default these can not be accurate enough to tell you PH change and are open for a large factor of human error. The color change in the indicating dye is only utilized as an approximate of the endpoint of titration. They are ok for getting a range of PH but not seeing PH change. On another note, I highly doubt that the PH is 8.0 ALL day, every day. The O2 cycle vs the CO2 cycle of your tank would render a PH change in its own right. Even on a reverse light cycle it is not enough to keep some swing out of the mix.

BTW: Seachem salt very well can lead to Alk problems. They greatly boost the borate concentration in their salt to a level of about 5-7mM. This is over a factor of 10 given what is in seawater and makes a significant problem in total alkalinity measurement and interpretations. It makes it really hard to know how much of your total alk is bicarbonate and carbonate and so it is hard to know if you are giving your corals what they need. This is why Seachem has unusually high alk recommendations. But they also have a test for borate and hydroxide alk.. Just one more thing they want to sell ya!!

 

[jetlink82]

I am using reef crystals salt.

 

[jimmystephens]

The best advice anyone gave me when i was first starting out was dont chase the numbers. U want them to be in range but dont get caught up in dumping tons of chemicals in ur tank to hit a certain #. U want it to be consistent, thats the key.

 

[acroholic]

JimmyStephens;940838 wrote: The best advice anyone gave me when i was first starting out was dont chase the numbers. U want them to be in range but dont get caught up in dumping tons of chemicals in ur tank to hit a certain #. U want it to be consistent, thats the key.

^ This.

 

[jetlink82]

That is what I am figuring out. I am not going to worry about getting exact numbers but will keep it within the range of what they should be around and just go with it.