View Full Version : Chemistry help
underpar
10/16/2009, 09:47 AM
In an effort do beat some hair algae growth, I am thinking about raising my calcium level to 450 ppm, the very top of Randy's recommended range. This target is suggested in http://www.bluezooaquatics.com/resources.asp?show=6 .
According to the reef chemistry calculator, a balanced alk level is about 4.45 meq/L., which is well above Randy's max of 4 meq/L.
Additionally, I assume this higher alk level will significantly increase the pH level above the suggested 8.1-8.3 range.
I would greatly appreciate any insights into this strategy and its ramifications.
Thanks, Fred
acrylic_300
10/16/2009, 10:49 AM
I think a lot of people that run their Ca at 450 run their Alk lower than the balance. On an average people run alk between 7-9.
I'm not sure raising Ca to 450 will do much for hair algae.
Randy Holmes-Farley
10/16/2009, 12:02 PM
I agree.
There is no desirability of having the alkalinity "balanced" to the calcium, so keeping it lower is fine.
FWIW, I'm doubt the elevated calcium will help algae at all.
balloonpilot
10/16/2009, 02:33 PM
Randy,
I though one had to keep the Alk up to 'aid' in the corals usage of Ca. Is this not true?
What would be the pro/con of running Alk at 8 instead of 10 ?
Thanks
bertoni
10/16/2009, 05:45 PM
Stony coral growth might be a tad slower at 8 dKH, and the pH will be a tiny bit lower. Also, there's less "headroom" so the daily low point of alkalinity might drop too low. Most likely, you'll never notice the difference, though.
Randy Holmes-Farley
10/17/2009, 07:02 AM
I agree.
I though one had to keep the Alk up to 'aid' in the corals usage of Ca. Is this not true?
Yes, but that only means one needs to keep it up to 7 dKH or so, not higher and higher just because calcium might be higher than normal. :)
balloonpilot
10/17/2009, 07:21 AM
Sound it sounds like a better position to be in is to target Alk at 8 to 9 rather than 9-10 ?
Randy Holmes-Farley
10/17/2009, 07:30 AM
Some folks are very concerned bout matching NSW at 7 dKH, especially the zeovit folks, but I generally recommend 7-11 dKH.
balloonpilot
10/17/2009, 07:48 AM
I had been using Seachem Reef Salt and setting Alk to 9.6 to 10. But I was doing this with the Salifert test kit and I wonder how much the Boron/Borate in Seachem would be throwing off the actual Alk measurement ?
balloonpilot
10/17/2009, 08:04 AM
One more question...
If the desired ALK is 7 to 11... Why would someone use IO Reef Crystals that was recently tested at 13 ? Why not use Red Sea Coral Pro which tested at 7 and supliment it to 8?
Sorry if too many new guy questoins :)
Randy Holmes-Farley
10/17/2009, 08:38 AM
There is a lot more to salt than alkalinity, calcium, and magnesium, and IO typically does not come out that high, IMO.
Also, starting alk in a salt mix has little bearing on the steady state alkalinity in a mature reef tank, where the inputs and outputs are high.
FWIW, I use only IO. :)
balloonpilot
10/17/2009, 08:57 AM
IO Reef Crystals - Cool.... That's what Im mixing up right now :)
But that leads to another question...
Im trying to mix to 1.026 and slowly adding salt to my 5 gal bucket. I got to 880 grams. When I measured this amount it was 1.027 (oops), but I let the probe sit for 10 minutes and it dropped to 1.0258.
What would cause readings to drop in a 5 gal bucket of new salt mix? I'm assuming I go with the final reading and not the initial spike?
I started out with 640grams, measured and worked my way up 40g at a time.
Im using a probe attached to my Profix contoller to measure SG
Randy Holmes-Farley
10/17/2009, 11:25 AM
It is a conductivity probe?
Changes in temperature impact such measurements, and the time it takes the probe to come to the water temp also impacts it.
balloonpilot
10/17/2009, 03:35 PM
Yes its a conductivty Probe connected to my Profilux and set to display as Specific Gravity.
So when I mix my water I've got it heated to tank temp, but I guess when I pulled some out in a glass cup to test, the water cooled off?
So SG rises as temp decreases...
Randy Holmes-Farley
10/17/2009, 03:42 PM
When you first put the probe in, it takes time to come to the water temp. The Pinpoint takes a few minutes, IME. My Orion only takes 15 seconds or so. But they all take time. That might or might not explain what you saw. Actual conductivity won't drop during salt dissolution.
I discuss temp effects and other issues here:
Using Conductivity to Measure Salinity
http://web.archive.org/web/20040604034508/http://www.aquariumfish.com/aquariumfish/detail.aspx?aid=1804
tatuvaaj
10/18/2009, 03:29 AM
balloonpilot,
You could take a glass of aquarium water, test the salinity and then put the glass into a refrigerator and retest after a few hours. If the temperature correction is "perfect" you should get the same salinity (but not true SG because it changes slightly with temperature). I would be interested in results :thumbsup:
Randy Holmes-Farley
10/18/2009, 08:19 AM
I've done that with my meters and they are not too far off between 80 deg F and 65 deg F, although I do not recall the exact changes I saw. They both report in mS/cm, not sg. Some meters allow different temperature corrections to be chosen, but those are high end devices. :)
tatuvaaj
10/18/2009, 08:26 AM
I was surprised that Profilux reports conductivity as SG ;)
I don't see how that would be preferable to salinity (or temp corrected conductivity) ?
balloonpilot
10/20/2009, 01:48 PM
The Profilux uses a Conductivity probe but you can tell it to "correct" for a manually set temp or tank temp correction and you can display it in "ms" or "sg".
So what is the 'prefered' way to measure / represent 'salt' content (salinity, conductivity, sg) ?
bertoni
10/20/2009, 03:33 PM
It's just a matter of personal preference. I use mS/cm, because that's what the PinPoint salinity probe reports, but either unit is fine. Just make sure the device is reporting corrected to a reference temperature of 25 C.
balloonpilot
10/20/2009, 03:38 PM
"Just make sure the device is reporting corrected to a reference temperature of 25 C. "
How do I do that. I mean I think I already set things up that way, but now I'm starting to have 2nd thoughts.
bertoni
10/20/2009, 03:49 PM
There might be a description in the manual. Otherwise, you could ask the manufacturer. Alternatively, you could get some of the PinPoint solution, and see what that measures. It should be at 53 mS/cn at 25 C. I would guess that the reference temperature is 25 C.
Randy Holmes-Farley
10/20/2009, 03:51 PM
The units of mS/cm are what is actually measured. Like a tape measure measuring inches. Anything else requires a conversion, like inches to numbers of sheets of paper in a stack of that height, and you have to have confidence in the conversion being accurate. Also, measuring anything else with it (like the conductivity of limewater) would necessarily be incorrect and confusing when measured in units relating to seawater specific gravity or salinity.
You can always check your device using the commercial Pinpoint 53 mS/cm standard = sg = 1.0264 = 35 ppt. A DIY can also be made if you have a good scale:
Reef Aquarium Salinity: Homemade Calibration Standards
http://reefkeeping.com/issues/2004-06/rhf/index.htm
balloonpilot
10/20/2009, 03:52 PM
So the trick is to get the test solution to 25C (77F)...
I'll have to double check how i set things up.
But either way - I did take some test solution, put on refract, let get to roomtemp and calibrated. Then tested that against readings from the probe.
tatuvaaj
10/20/2009, 04:07 PM
I prefer salinity calculated from conductivity :thumbsup: I don't like SG because it is so easily confused with density.
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