Aquarium Chemistry Question? Ask the Doctor!

[Randy Holmes-Farley]

Thank you so much.

You're welcome.

Happy reefing.

 

[Randy Holmes-Farley]

@Randy Holmes-Farley

First, It appears that seachem kalk (according to their site) is not the same as pickling lime, as they claim it doesn't effect alk. Why?

It is exactly the same material as pickling lime. I can only suppose it is because they do not have a good understanding of the chemistry of their product. They are wrong in the first sentence below, and the second is kind of vaguely right/wrong.

http://www.seachem.com/reef-kalkwasser.php

"Increases pH with no impact on carbonate alkalinity"
"Kalkwasser solutions maintain calcium directly and carbonate alkalinity indirectly."​

As is, in the bottle, the hydroxide supplies total alkalinity and not carbonate alkalinity, but the instant the hydroxide mixes into seawater (instant here meaning, probably, microseconds or less), most of the added hydroxide converts bicarbonate into carbonate, raising carbonate alkalinity immediately. Some of it stays as free hydroxide, raising pH but not carbonate alkalinity, and some converts carbonic acid into bicarbonate (increasing carbonate alk).

Then over time (up to hours) this new set of carbonate system chemicals pulls in more CO2 from the air, reacting some of the hydroxide with CO2 to form bicarbonate (keeping total alkalinity unchanged and increasing carbonate alkalinity a tiny amount) and some new CO2 reacts with carbonate to form bicarbonate (no effect on carbonate or total alkalinity).

 

[Randy Holmes-Farley]

Second, I'm (newly) dosing enough vinegar (52 ml per day of seachem kalk saturated vinegar treating 100 gallons of water) to keep nitrates in check. It seems to be holding my alk steady despite their claim of it not adding alk. Why? My only reasoning behind adding kalk to the vinegar is to keep ph elevated while adding that volume of vinegar. I was planning on dosing 3 part as needed to maintain whatever needs adjusted from there.

It adds alkalinity for the reasons I gave above.

Thirdly, I'm not doing water changes, so I was wondering what could potentially build up with impurities of their kalk, or if you think there is enough impurities for me to change my game plan now before a buildup could occur? Maybe I'll remove the kalk from the vinegar and see where my ph ends up. What's your take? Thanks

Assuming the solution is still saturated in calcium hydroxide (that is, no more dissolves), then I do not think you are likely to build up any more impurities this way than any other dosing scheme for calcium and alkalinity.

When i was manually dosing vinegar, this was how I dose it, saturated with calcium hydroxide.

 

[Scott.h]

It is exactly the same material as pickling lime. I can only suppose it is because they do not have a good understanding of the chemistry of their product. They are wrong in the first sentence below, and the second is kind of vaguely right/wrong.

http://www.seachem.com/reef-kalkwasser.php

"Increases pH with no impact on carbonate alkalinity"
"Kalkwasser solutions maintain calcium directly and carbonate alkalinity indirectly."​

As is, in the bottle, the hydroxide supplies total alkalinity and not carbonate alkalinity, but the instant the hydroxide mixes into seawater (instant here meaning, probably, microseconds or less), most of the added hydroxide converts bicarbonate into carbonate, raising carbonate alkalinity immediately. Some of it stays as free hydroxide, raising pH but not carbonate alkalinity, and some converts carbonic acid into bicarbonate (increasing carbonate alk).

Then over time (up to hours) this new set of carbonate system chemicals pulls in more CO2 from the air, reacting some of the hydroxide with CO2 to form bicarbonate (keeping total alkalinity unchanged and increasing carbonate alkalinity a tiny amount) and some new CO2 reacts with carbonate to form bicarbonate (no effect on carbonate or total alkalinity).

It adds alkalinity for the reasons I gave above.



Assuming the solution is still saturated in calcium hydroxide (that is, no more dissolves), then I do not think you are likely to build up any more impurities this way than any other dosing scheme for calcium and alkalinity.

When i was manually dosing vinegar, this was how I dose it, saturated with calcium hydroxide.

Thank you for the logical response. I assumed something was goofy with their claims, hence my reason to ask.

I knew you dosed a large amount of vinegar, but I didn't realize you were saturating it in kalk. I ended up where I'm at by accident, but it's really working well so far. I've seen a noticeable jump in coralline, so that's a good sign. I'll give it a few months and send in a water sample. Thanks again for the help!

 

[Randy Holmes-Farley]

Thank you for the logical response. I assumed something was goofy with their claims, hence my reason to ask.

I knew you dosed a large amount of vinegar, but I didn't realize you were saturating it in kalk. I ended up where I'm at by accident, but it's really working well so far. I've seen a noticeable jump in coralline, so that's a good sign. I'll give it a few months and send in a water sample. Thanks again for the help!

You're welcome.

Happy Reefing.

 

[SDReefer]

Hello Dr. Holmes-Farley,
I am looking to buy cyanoacrylate gel in bulk and want to make sure that it is safe for my reef tank. The product says that it is composed of ethyl-2 cyanoacrylate. Is it safe to use in my tank or should I just play it safe and buy a bunch of the regular super glue gel tubes?

Thanks!!

 

[Randy Holmes-Farley]

That's certainly a suitable monomer for a cyanoacrylate adhesive. It will be quite runny without any thickening agent in it.

If you use a lot, I'd run extra GAC in the tank, but experience shows that it is generally OK.

 

[SDReefer]

Thanks!!!

 

[Randy Holmes-Farley]

You're welcome.

Good luck.

 

[Crashjack]

Another alkalinity problem... I'm stuck in a "catch 22" situation with alkalinity. My pH was running around 7.75 - 7.9 and kalk additions via my ATO pump through a kalk stirrer would increase alk significantly (from around 8 dkh to around 10 dkh in less than a week), while not affecting Ca much (staying around 450-460 ppm). The water would become saturated, and I would start getting precipitation. Magnesium would drop some in a week's time, maybe 15-30 ppm, and I would adjust if it ever dipped below 1400 ppm. My tank looked ok, but I was getting almost no coral growth. Either the alk spikes or the low pH also caused my rainbow acans to become brown acans.

The flip side is now I've added a CO2 scrubber and am still running kalk with my ATO/stirrer.. My pH varies from a little under 8.1 to a little under 8.3. I'm getting coral growth and my rainbow acans are "rainbows" again, but now my alkalinity is tanking (down 1+ dkh in 5 days). However, my calcium is dropping very little (down 10 ppm in 7 days, which might just be the way I held my mouth when I did the test), and magnesium actually went up 15 ppm, which again might just be some slight variation in the test. I tested alk twice with a Hanna checker and once with an API test kit and got very similar results. Because my magnesium hasn't changed much since I added the scrubber, I got a new Mg test kit but am still seeing the same results. The bottom line is, I went from low pH with precipitation, my alk spiking, Ca remaining fairly constant, and Mg dropping some; to good pH with alk dropping a lot, Ca dropping slightly, and Mg staying the same. I haven’t added any new corals since before I added the scrubber. Does this make sense?

 

[Scott.h]

Another alkalinity problem... I'm stuck in a "catch 22" situation with alkalinity. My pH was running around 7.75 - 7.9 and kalk additions via my ATO pump through a kalk stirrer would increase alk significantly (from around 8 dkh to around 10 dkh in less than a week), while not affecting Ca much (staying around 450-460 ppm). The water would become saturated, and I would start getting precipitation. Magnesium would drop some in a week's time, maybe 15-30 ppm, and I would adjust if it ever dipped below 1400 ppm. My tank looked ok, but I was getting almost no coral growth. Either the alk spikes or the low pH also caused my rainbow acans to become brown acans.

The flip side is now I've added a CO2 scrubber and am still running kalk with my ATO/stirrer.. My pH varies from a little under 8.1 to a little under 8.3. I'm getting coral growth and my rainbow acans are "rainbows" again, but now my alkalinity is tanking (down 1+ dkh in 5 days). However, my calcium is dropping very little (down 10 ppm in 7 days, which might just be the way I held my mouth when I did the test), and magnesium actually went up 15 ppm, which again might just be some slight variation in the test. I tested alk twice with a Hanna checker and once with an API test kit and got very similar results. Because my magnesium hasn't changed much since I added the scrubber, I got a new Mg test kit but am still seeing the same results. The bottom line is, I went from low pH with precipitation, my alk spiking, Ca remaining fairly constant, and Mg dropping some; to good pH with alk dropping a lot, Ca dropping slightly, and Mg staying the same. I haven’t added any new corals since before I added the scrubber. Does this make sense?

You're chasing numbers to what could actually be testing error with your kits in accuracy. If you're struggling with low ph, kalk could help. When you were using kalk your calcium was absolutely fine. Stability is more important then hitting a specific number. If your calcium is around 420 or above you're fine. All your numbers are within an appropriate range. Tweaking can cause more harm then good as well. Get a different test kit then API, as the tollarence isn't close enough compared to the others test kits available. The important thing is to know your alks daily depletion and keep it stable. Add the other elements as needed. Maybe mg once a week. I'd be surprised if mg dropped much, or at all. Mg test kits are known to be fairly inaccurate as well.

 

[Randy Holmes-Farley]

Another alkalinity problem... I'm stuck in a "catch 22" situation with alkalinity. My pH was running around 7.75 - 7.9 and kalk additions via my ATO pump through a kalk stirrer would increase alk significantly (from around 8 dkh to around 10 dkh in less than a week), while not affecting Ca much (staying around 450-460 ppm).

That's what you'd expect, if you consider a range of 10 ppm in calcium to be about the same. Limewater adds only 14 ppm of calcium for each 2 dKH of alkalinity. So you wouldn't expect to really notice much calcium rise for that alk rise.

The flip side is now I've added a CO2 scrubber and am still running kalk with my ATO/stirrer.. My pH varies from a little under 8.1 to a little under 8.3. I'm getting coral growth and my rainbow acans are "rainbows" again, but now my alkalinity is tanking (down 1+ dkh in 5 days). However, my calcium is dropping very little (down 10 ppm in 7 days, which might just be the way I held my mouth when I did the test), and magnesium actually went up 15 ppm, which again might just be some slight variation in the test. I tested alk twice with a Hanna checker and once with an API test kit and got very similar results. Because my magnesium hasn't changed much since I added the scrubber, I got a new Mg test kit but am still seeing the same results. The bottom line is, I went from low pH with precipitation, my alk spiking, Ca remaining fairly constant, and Mg dropping some; to good pH with alk dropping a lot, Ca dropping slightly, and Mg staying the same. I haven’t added any new corals since before I added the scrubber. Does this make sense?

The raised pH increased the demand for calcium and alkalinity, and the limewater is no longer keeping up. You need to either deliver more, or add another supplementation method, such as a two part (that would be my recommendation). I also doubt the magnesium really dropped that much. At max, it's consumption is about 1/10th of the calcium consumption rate, although since you are dosing calcium, you need to take that into account in figuring an expected drop. A few ppm a week is likely.

 

[Crashjack]

Thanks Randy! My thought was that a drop of 1+ dkh would result in a larger drop in Ca than I've been seeing but if 14 ppm alkalinity (approx. .78 dkh) is equivalent to 10 ppm Ca, I guess it makes sense.

 

[Randy Holmes-Farley]

You're welcome.

Happy Reefing.

 

[cincyreef]

Hi Randy! I've been searching for awhile, and I can't find the thread that talks about matching your water change water to the tank concerning ALK. For example I'm trying to see what effect it would have on my tank if I add 5 gallons of water with ALK at 10.5, to my existing tank which is 25 gallons of water and ALK is at 9.5. Thanks for the help, and I hope you understand what I'm saying. I'm looking for the math behind it.

Thanks,
Brent

 

[redfishbluefish]

So if I understand correctly, you take out 5 gallons from your DT, so you now have 20 gallons of water at 9.5. You add 5 gallons back into the DT that is at 10.5, so the math looks like this:

(9.5 x 20 g) + (10.5 x 5 g) = ??/25g
( 190 ) + ( 52.5 ) = 242.5/25 = 9.7 dKh

 

[Randy Holmes-Farley]

FWIW, alkalinity of a combination (like post water change) when combining two liquids is just the weighted average of the two values.

 

[Sagecritter4life]

Hey Randy [emoji6] have a question for the master. Been running my first dosers and My alk is 8.1-8.2 after tweaking couple weeks but my calcium seems stay around 450 is that okay or getting out of whack? Temp 78F @ 1.026 thanks.

 

[Randy Holmes-Farley]

Calcium at 450 ppm is just fine. If it starts pushing 500 ppm, I'd back off on that doser.

 

[Sagecritter4life]

Calcium at 450 ppm is just fine. If it starts pushing 500 ppm, I'd back off on that doser.

Awesome thanks still trying to wrap my mind around all this stuff..chuckle