Let's talk about Alkalinity, Calcium and Magnesium in an SPS Tank

[MCsaxmaster]

I aim to please

[khoivo1]

thanks alot,,i learned some thing today ,,,
any way what is acceptible range of
ALK?? 7.0dkh-11dkh??
CAl?? 360--450???
mag?? 1260-1400???
is that right?? thanks

[MCsaxmaster]

Yeah, that's probably not bad. For magnesium I'd shoot for right around NSW levels: 1250-1350 ppm seems appropriate (NSW ~1285 ppm). There's no reason to think higher magnesium is actually doing anything good, while low magnesium can cause excessive abiotic CaCO3 precipitation problems.

For calcium I'd shoot for at or perhaps just slightly higher than NSW: 400-450 ppm seems appropriate (NSW ~ 412 ppm). There's very little reason to think that calcium higher than that actually encourages faster calcification in most corals. Below 400 ppm, however, you may start running into calcium limitation of calcification, but calcification is only reduced slowly from ~400 down to maybe ~300 ppm. From 300 to 200 ppm calcifcation drops off much faster. Below 200 ppm calcification drops like a rock.

I'd maintain a minimum of 7 dKH total alkalinity (assuming normal borate levels). NSW has ~6.6 dKH total alk. Critters do just fine in that, but most certainly calcify faster with higher alk. I've generally had the best success maintaining TA in the neighborhood of 9-12 dKH.

Oh, and the NSW parameters all assume standard sea water (35 ppt, 25 C, 1 atm, etc.).

Chris

[Marshall Haith]

I don't think this issue has been discussed.

Problem: annoying buildup of what looks like calcium precipitate on glass (white chalky stuff that is hard to scrape off), mainly, but not exclusively, on sides where the flow from the power heads is directed and on front middle glass where the flow from the two heads meets.

Parameters:
50 g tank, 5 g sump
ph around 8.0
calc around 325
dkh around 6.5 to 7.0
mag at around 1280-1300
water changes of 8% or so/week
light coral load

Trying to raise calc to around 425 without much luck. I'm using 2-part solution, adding 100 ml of calc/day and 100 ml of buffer. These are added in 50 ml doses. each in about a half liter of water, to sump through a gravity drip at around 2 drips/sec.

The values are around 2.5X what I think Randy suggests for this size and type of tank, but the calcium level isn't changing much (after about 2 gals of mix have been added over several weeks). The precipitate is terribly annoying and time consuming to remove and suggests that I may be adding too much. I've checked the calk, ph and dkh measures against store measures and my son's kits.

The heater glass did have a substantial buildup, but I cleaned it two weeks ago, and it doesn't seem to be accumulating a film very quickly. I haven't checked the pumps internally, but they don't look bad at all on the outside.

Befuddled.

[MCsaxmaster]

Huh--could you post a picture? Accumulating preferentially in areas of strong flow sems strange.

cj

[Aquarist007]

Originally posted by Sk8r
Bertoni came up with an interesting observation: if you are supplementing [an dI hope I'm quoting him right] with 2-part or Kent's or whatever, you're actually adding some mg.

If you are supplementing with kalk, you are not, because there is no mg in kalk.

So if the corals are using mg, and you are not supplying it via your supplement, the net effect is that you are losing mg and need to supplement more.

That may reconcile Randy with Bertoni. Bertoni makes those comments in the thread I linked to above.

I agree with your statements.
Corals actually don't use that much magnesium--regular water changes with the appropriate salt mix can help keep the mag up

Look at the differences in levels in the different mixes that Billybeau has put together

http://www.reefcentral.com/forums/sh...readid=1287118

[Marshall Haith]

Huh--could you post a picture? Accumulating preferentially in areas of strong flow seems strange.

c j

Thanks Chris. Posted are a couple of photos, the closeup being of the center front glass. You are right. The calc buildup is actually to the side of the powerheads and below them, not in the output stream, so the water is pretty slow-moving there. In front, the output streams from the two powerheads meet, so they cancel one another, and the flow is pretty slow there also.

mh

[Aquarist007]

Originally posted by Marshall Haith
Huh--could you post a picture? Accumulating preferentially in areas of strong flow seems strange.

c j

Thanks Chris. Posted are a couple of photos, the closeup being of the center front glass. You are right. The calc buildup is actually to the side of the powerheads and below them, not in the output stream, so the water is pretty slow-moving there. In front, the output streams from the two powerheads meet, so they cancel one another, and the flow is pretty slow there also.

mh

To Reef Central

could you possible take out an album on www.photobucket.com
you upload your pictures to your album
under each pic is four codes
you use the fourth code----the "img" code to copy and paste into your posts

You get a much bigger and clearer picture when doing that then using the gallery here.

[Marshall Haith]

could you possible take out an album on www.photobucket.com

Ok, here they are.

mh

[IMG][/IMG]

[IMG][/IMG]

[Aquarist007]

Originally posted by Sara B
I do use a Salifert Magnesium test kit. I also run a Kalk reactor on both systems and drip with top-off water 24/7. The reactors stir the Kalk 4 times a day for 15 minutes at a time. I have a basement fishroom and my PH remains in the range of 7.8 to 8.0 as the A/C running all summer has an effect on it's level. In the fall and winter its more in the 8.2 range as I have a vent that's open for fresh air in the room.

had the same problem last summer. I keep a window open in the basement 24/7. That kept not following below 8.0.This spring I added a second 37 gal fuge--that keeps the pH at 8.19
If you can't keep the window open vent the skimmer to the outside--that will make a difference

[Aquarist007]

Originally posted by Marshall Haith
Ok, here they are.

mh

[IMG][/IMG]

[IMG][/IMG]

much better

I would assume your low dkH values are behind the precipitation
You should be running 10-11.5 dkH

[Marshall Haith]

I would assume your low dkH values are behind the precipitation

Hmm. I was using this article by Randy Holmes-Farley as a guide: http://reefkeeping.com/issues/2005-07/rhf/index.php. The article indicates that increasing alk exacerbates the problem of calc precipitation, so I was shooting for the lower end of the operating range for alk.

mh

[JB NY]

I agree, I've never had ca precipitation with low alk, only high.

[fishdoc11]

Me too, only high

FWIW in the pics above it looks a bit more like some sort of coraline (or something else) than Ca precipitation.

Chris

[Aquarist007]

but at what levels did you get the precipitation?

IMO keeping the alk between 8-11 is better then keeping it in the low 7's?
I am sure Randy mentioned something about low alkalinity

[Marshall Haith]

Actually, I've had the dkh in the 8-10 range, and I had the same problem.

mh

[MCsaxmaster]

Marshall,

How are you measuring pH?

I would assume your low dkH values are behind the precipitation

Huh-uh. All else equal (e.g., pH, temperature, precense of nucleation sites, etc.), with lower carbonate alkalinity you'll have lower rates of CaCO3 precipitation.

The rate of precipitation depends mostly on saturation state (assuming there are available nucleation sites, which is probably a good assumption in an aquarium full of pieces of CaCO3 rock/sand ). Saturation state, at a given temperature, salinity, pressure, is described by:

omega = [Ca++][CO3=]/Ksp*

where [Ca++] is the calcium concentation, [CO3=] is the carbonate concetration, and Ksp* is the solubility product (adjusted for use in sea water). If calcium goes up, satuation state goes up proportionally. If carbonate goes up, saturation state goes up proportionally. Carbonate concentration is controlled by carbonate alkalinity and pH (all else equal). The higher the alkalinity, all else equal, the more carbonate there is. The higher the pH, all else equal, the more carbonate there is. If both alkalinity and pH go up, carbonate goes up more still. You get the idea.

[Aquarist007]

Originally posted by MCsaxmaster
Marshall,

How are you measuring pH?

I would assume your low dkH values are behind the precipitation

Huh-uh. All else equal (e.g., pH, temperature, precense of nucleation sites, etc.), with lower carbonate alkalinity you'll have lower rates of CaCO3 precipitation.

The rate of precipitation depends mostly on saturation state (assuming there are available nucleation sites, which is probably a good assumption in an aquarium full of pieces of CaCO3 rock/sand ). Saturation state, at a given temperature, salinity, pressure, is described by:

omega = [Ca++][CO3=]/Ksp*

where [Ca++] is the calcium concentation, [CO3=] is the carbonate concetration, and Ksp* is the solubility product (adjusted for use in sea water). If calcium goes up, satuation state goes up proportionally. If carbonate goes up, saturation state goes up proportionally. Carbonate concentration is controlled by carbonate alkalinity and pH (all else equal). The higher the alkalinity, all else equal, the more carbonate there is. The higher the pH, all else equal, the more carbonate there is. If both alkalinity and pH go up, carbonate goes up more still. You get the idea.

gottcha---thanks very much for the detailed answer

[gary faulkner]

Originally posted by capn_hylinur
gottcha---thanks very much for the detailed answer

Capn,

Sounds Greek to me too.

[MCsaxmaster]

Greek, geek, whatever

[fishdoc11]

Geek here

[Aquarist007]

Originally posted by gary faulkner
Capn,

Sounds Greek to me too.

I wasn't kidding---I did follow the drift--Mcsaxmaster does explain chemistry well

[Zedar]

Originally posted by MCsaxmaster


I'd maintain a minimum of 7 dKH total alkalinity (assuming normal borate levels). NSW has ~6.6 dKH total alk. Critters do just fine in that, but most certainly calcify faster with higher alk. I've generally had the best success maintaining TA in the neighborhood of 9-12 dKH.

Oh, and the NSW parameters all assume standard sea water (35 ppt, 25 C, 1 atm, etc.).

Chris

What is your opinion on ULNS? People that maintain ULNS through carbon dosing have experienced basal STN when running their systems above 8 dkh.

I myself run one of these systems and have experienced this first hand.

[MCsaxmaster]

ULNS?

[Zedar]

dbl post