FAQs on Calcium and Alkalinity in Seawater,
Related Articles: Calcium
and Alkalinity Explained by Anthony Calfo, Calcium, Biominerals, The Use of Kalkwasser
by Russell Schultz, Calcium
Maintenance, Marine Water
Quality, Magnesium in
Seawater, Strontium in Seawater,
pH, Alkalinity, Marine Alkalinity, Live Sand, Marine
Substrates, Reef Systems,
Related FAQs: Ca/Alk 1, Ca/Alk
3, & FAQs on: The Science of
Calcium & Alkalinity, Importance, Measure, Use of
Additives, Troubleshooting/Fixing, Products, & Calcium,
& FAQs on Calcium: Rationale/Use, Calcium Measuring/Test Kits, Sources of Calcium, Calcium Supplements, Dosing, Chemical/Physical Interactions, Troubleshooting/Fixing, &
& FAQs on Calcium Reactors: Rationale/Use, Selection, Installation, Operation, Media, Measuring, Trouble-Shooting, By Makes/Models, & pH, Alkalinity, Marine Alkalinity, Marine Alkalinity 2, Marine Alkalinity 3,
Inputs: Mmm, substrates (rock and sand), synthetic
(and natural to a smaller extent) sea salt, supplements of
several sorts (Kalkwasser, commercial prep.s, foods/feeding,
calcium and other reactors,
Outputs: precipitation/chemical interactions (sped
up with low pH), biomineralizing life,
Dosing vs. calcium reactor/Kalk top off
Recently I have had a few issues with my aging aqua medic calcium reactor.
It has served me well but with a few panic Kalk additions because of low
alkalinity I had a massive precipitation issue where the excess calcium baked
itself to my system pump impeller wrecking it.
Not my finest aquarist hour I assure you. I have seen some advanced systems
using dosing pumps for the maintenance of Kalk mg and ca (and it seems to be
very precise and would assist me long term I feel).
<... the most appropriate, best available technology per your system,
It is as you know a huge cost and I was wondering whether my existing setup is
suitable enough or is getting a bit old school and I need to invest?
Btw my stock is large Euphyllias. Caulastrea and blastos plus some leather
<.... the wife used to distribute Knop Products in N. Am. for five years...
I'd go w/ simple A/B additions here. Likely SeaChem's Fusion line>
<Pleasure. Bob Fenner>
DSB, Calcium and Alkalinity 12/13/10
Good Morning Crew.
<Hello Sarah, but not a good morning. We have snow up the kazoo,
it's 9 degrees out, and I need to blow out the driveway.>
I hope this finds everyone well. I have made it for a year with my 90
gallon saltwater tank learning and having a lot of fun along the way.
Not to mention lots of mistakes in stocking. My system itself has
worked for me. I'm still using a wet dry filter with skimmer rated
for 300 gallons. Have a HOB power filter that I use to add carbon.
Should I remove this HOB filter?
<Many hobbyists use these, canister filters, and media reactors as a
means of chemical filtration. Why do you want to remove it?>
I know the wet dry is a nitrate factory but I have had luck with
keeping them low and don't want to tear down the whole system to
switch to my dream system.
<I would remove the bio balls over a period of two weeks if you are
using such biological filtration media, it isn't necessary with
That will come later. I do water changes of 10 gallons every Friday and
also change the pad in the wet dry at that time. After reading about 5%
water changes twice a week'¦.well I'm thinking about doing
this Tues and Friday. It just sounds easier then what I am doing.
<Twice a week is overkill, once a week is plenty, and my schedule is
10% every two weeks.>
For the last month or so I have seen my Nitrates start to climb. Not
high but staying on top of things. So I decide that a deep sand bed
would be a good idea. I have 1.5 inches of crushed coral and started to
add size zero white sand to the top, on one side. Thing is I added 1.5
to 2 inches on that one side before reading that I should have added
Â½ of that every two weeks or so. Are my worms, pods and all
those good critters I saw going to make it or did I just wipe out
Â½ my sand bed?
<You should be OK here.>
And this is what is in my tank: Flower Pot Coral that is growing,
Bubble Coral, Star Polyps, Pulsing Xenia, Eagle Eye Polyps, Mushrooms
that don't fully open and have never looked great. Not sure why or
what to do with them at this point. Lantern Bass, Yellow Tang, Bi Color
Angel, Hippo Tang, Marron Clown, Sixline Wrasse, Ocellated Dragonet,
Pistol and Watchman Goby . Cleaner Shrimp, Snails, Hermit Crabs,
Feather Dusters, Urchin and Fighting Conch. Everything looks good and
is doing well except the Mushrooms.
<Likely allelopathy issues here. May want to move any corals that
are near the mushrooms.>
Here are my numbers'¦.PH 8.2, Ammonia and Nitrite 0, Nitrate
10 not really high but don't want to see it climb,
<Actually 5-10ppm of nitrate is beneficial for many corals and
clams. I would not strive to keep it at 0.>
Calcium 440, Phosphate 0.5, just tested kH at 14.
<Too high, I'd try to keep around 7-9dKH.>
I had never tested kH before but decided to do so because I have been
using Reef Builder, Reef Complete and Reef Plus in my tank for the last
4 months on the advice of LFS. Corals all are looking good and showing
growth accept the mushrooms. Fish are active and have all shown growth
as well. Chemistry is frustrating so I try to keep it simple....I was
reading your article on understanding Calcium and Alkalinity and see
that using Liquid calcium in not a good idea long term and kH being 14
in a little high. So with adding a deep sand bed and continuing to
test, should I drop these supplements and switch to Kalkwasser? How do
you add it?
<Actually, I'm not a fan of using Kalkwasser, it can create
problems with pumps (excessive calcium buildup), and can dangerously
raise pH if not dosed properly. What I've been happy with using the
last year or so is Tropic Marin's Alka Balance. This product
maintains calcium and dKH at acceptable levels, although I do
supplement occasionally with a marine buffer. The only other additive I
use is magnesium which is an important element to maintain when keeping
I really don't want to add a calcium reactor to this system.
<I don't blame you, the less to mess with, the better.>
You see I have this plan of upgrading this tank but won't be able
to for another year or two for what I have planned. So I don't want
to put expensive equipment into a system that has been working well
Even though the Liquid supplements are easy to use and seem to work I
don't want to see future problems from its use. What are your
<Liquid calcium supplements are OK to quickly raise calcium levels,
but I would not use long term.>
Thank you and stay well.
<Oh I will and you're welcome. James (Salty Dog)>
Re DSB, Calcium and Alkalinity 12/13/10
Sorry to hear about your winter wonderland. Honestly I am jealous. Wish
you could send it my way.
<I just got in from blowing out a 85'x16' drive. The temp is
9 degrees with a "feel like" of -5. Could you tell me what is
so wonderful about that? Where do people get this "winter
wonderland" from....must have never experienced it. HAH!>
I do have live rock and have thought about removing the Bio Balls but
again the thought of messing with something that is working has stopped
me. This is something I have been back and forth with for some time. I
know some put live rock in as they remove the Bio Balls. Do you
recommend this or leaving the filter empty?
<I'm not saying you need to do this, is entirely up to you.
Wet/dry systems using bio balls are a nitrate factory only because the
system is so darn efficient at denitrification. As long as your
nitrates stay somewhere near 10ppm, as you say, leave well enough
Would it be possible to store a chocolate chip star fish in there? For
harlequins in another tank : )
<Sure, as long as you ensure the starfish doesn't get sucked
into the pump intake.>
I'm confused about your water change recommendation. WetWebMedia by
Scott Fellman "The Perfect Water Change Regimen". Five
percent twice a week.
Good for corals and happier fish.....is this not so?
<Yes, it is so, but I don't feel this is an absolute necessity
to maintain a healthy tank providing the tank
is not overstocked, overfed, and an efficient protein skimmer is in
use. Mmm, I don't recall you mentioning
the use of one.>
Also have tried to move the mushrooms away from corals but can't
seem to find a happy place for them. Maybe its time to find them a new
I will check into Tropic Marin's Alka Balance. The less supplements
or what ever I'm adding the better.
<Is exactly how I feel about it. It's unbelievable how many
additives/products are out there, and all
promising to make your tank a dream system.>
Am I correct that only water changes will lower the alkalinity over
<Yes, is the safe way to do this although acid buffers will lower
the dKH, and I would advise against
Thanks James, enjoy that snow.
<Grrrrrrrrr! Will NOT enjoy the snow, but you're welcome Sarah.
James (Salty Dog)>
Re DSB, Calcium and Alkalinity 12/13/10 - 12/14/10
I have experienced your snow. Lived in the UP for a long time.
Don't see as much as I used to but we still get it. I'm just
one of those nuts who love snow.
<Nice to look at, that's all. I live in mid-Michigan and am
quite familiar with the amount of snow the UP can get in one winter.
Anyway, looking at the Tropic Marin Alca Balance. It is hard to
Looks like I would have to order it.
<Yes, much cheaper that way as well.>
It is supposed to keep Alkalinity at 6 to 9 and Calcium at a natural
<Yes, providing your tank is not overstocked and/or produces an
excessive amount of acids such as uneaten food, nitrates, etc.>
That's about 420 correct?
<Well, that all depends on the dosing level, something you will need
to monitor for a while until you
reach a happy medium, but I would try to maintain 380-400ppm. I'd
start with the recommended dose and test weekly. You may have to
increase or decrease the dose depending on your test results. Do ensure
you magnesium levels are maintained. Briefly, calcium loving inverts
need this to be able to absorb the calcium that is available to
From all the reading I have done we should keep dKH at 9 to 12. Sea
Water is 7 to 9.
So which is better and why? Should there be a reserve in our
<In heavily/moderately stocked fish only systems, I would strive to
keep dKH levels at 9-10 for a better reserve as pH swings can more
easily occur in these type systems. In well maintained reef systems
with a low to moderate fish load, 6-7 dKH is much better as it helps
prevent calcium precipitation and creates a balance more akin to what
is found on the reefs. I had asked Lou Ekus/Tropic Marin about this
product as to maintaining dKH/calcium levels and I will post his reply
"Hi James, sounds like you're right on track here <as to
the use of ALKA-Balance as the sole means of maintaining Ca/dKH>.
The thing about the ALKA-Balance is that it will 'lower' dKH in
time. I'm not sure that continued use of it as the only Ca source
would 'maintain' a dKH of 7. Using it will certainly help take
a high dKH and bring it down to that range, but 'overuse' might
lower the dKH to the range you're in. It sounds like your plan is
perfect. However, I would keep an eye on my dKH after going back to use
it to see if it continues to drop. If it does, I would alternate doses
with Bio-Calcium to help maintain that dKH around 7. Let me know how
you make out.
Oh, keep an eye on that Ca level. Letting it get up to 550 will just
cause you headaches!
Director of US Operations
<You're welcome. James (Salty Dog) >
calcite/Corosex 9/15/08 This is
more of a comment than a question, but.... I was experiencing high ALK
(16/17) with about 450 ppm calcium. Much of the written material
indicated this was not a likely pairing of conditions. The root cause
was that I have an acid neutralizer bed for my well water system that
has a mixture of calcite/Corosex (calcium carbonate and magnesium
oxide) such that the salt water as mixed was 16/17. I believe in these
mixed neutralizer systems the magnesium oxide is the more soluble
material. Using DI water solved this such that the makeup water is now
more like 12 dKH and it should dilute over time. I haven't been
tracking my magnesium level, but it is likely high. <Agreed.
Hopefully within ratio. Bob Fenner>
High Calcium & Alk Hello & Good Day! <Good day to
you> I've read all through the Calcium and Alk FAQs and
they've added to my confusion. Here's the scenario;
Tank is 75gal with 75lbs LR and DSB. Tank completed it's
cycle 10days ago. Since then I've added 2 dozen snails
and 1 dozen hermits over the course of seven days. A few
days ago I decided to start testing Calcium and Alk to see where I
stood and to make sure my Coralline was going to do well. Day 1 of
testing Calcium / Alk in main tank = Cal 210, Alk
11.5 So I added some Tropic Marin Bio-Calcium.
'Contents are calcium ions, hydrogen carbonate and all 70 trace
elements found in natural sea water.' Day 2 of testing Calcium /
Alk in main tank = Cal 300, Alk 13.8 tested
Replacement Water ( 10gals ) = Cal 270, Alk 9.9 Added Tropic
Marin to both. Day 3 ( Today ) of testing Calcium / Alk in main tank =
Cal 315, Alk 15 tested Replacement Water = Cal 255, Alk
12.2 '¦So'¦ I --thought- that as one raised the other
would lower but it actually looks like both are rising in my main
tank. I'm adding the Tropic Marin as directed but now
that my Alk is out of the recommended range I'm leery of adding
anymore. <The Tropic Marin could be raising both.> What should I
do? Wait a couple days and test again? Use a
product to lower Alk? If so, what? I'd like
to start placing some actual fish in the system but not until I can
understand and handle what I've bitten off so far. Thanks for your
time! Scott <I would start by doing several large water changes
(25%-50%) over the next 7 to 10 days, without adding
supplements. This should dilute the
imbalance. Then resume supplementation with a 2part calcium
supplement, Tropic Marin, or Kalk. Best Regards,
Smooth sailing on Ca & ALK? 5/5/03 What is your take on
this? For months I used two part b-ionic with good success
in my 29 gallon reef tank. (Prior to that, for a couple of
years, I tried the balancing act of adding calcium and buffer
separately.) Anyway, out of the clear blue sky, I have found
the calcium and PH levels staying extremely stable and I have stopped
adding the bionic. (Will continue to monitor of course.)
<Hmmm... you haven't mentioned you ALK (hardness dKH) and I
wonder if your test kits are accurate (over 6 months old for
reagents?). Before you stop any crucial supplementation... please
confirm you water quality on other test kits for reference> The tank
is skimmed, strong circulation, constant small water changes, live
rock/sand and the best husbandry possible. (Bordering on
obsessive.) No supplemental additives. only corals are
corallimorphs, no algae. light fish load, no problems
whatsoever. Could this be the reasons the tank stabilized?
<perhaps... simply a low demand/bio-load> Thanks for the input.
William <best regards, Anthony>
- Ca/dKH Questions - Dear WWW Crew, <Greetings, JasonC
here...> Thanks for your advice in the past and the great web site.
I have looked through all of the calcium FAQ's and am unsure how to
proceed with my own reef. I have a 4 year old 75 gal reef with 80lb
live rock and a 30 gal refugium with a 7 in DSB. I have several LPS
corals and a variety of soft corals with a few small fish. The corals
are doing very well (I've divided my frog spawn several times). I
have a Turboflotor 1000 skimmer and a Korallin calcium reactor. I do 5
gal water changes monthly and top up water with a "NURCE"
device using buffered R/O water. My chemistries are pH 8.3 (day)/ 8.0
(night), dKH 9.0, Ca 400, Mg 1300, nitrite/ammonia/nitrate 0. Since
getting the Ca reactor the Ca/dKH have been much more stable (compared
to chasing levels with supplements alone) but NOT optimal-Ca 325 and
dKH 8. To boost this up I use Kent Super buffer 4 tsp. every 4 days and
add Kent turbo Ca to the make up water (~3/4 tsp. per day). I have
tried Kalkwasser repeatedly in the past with unimpressive results. In
addition I frequently work over night and cannot dose stuff when the
lights go out very often. This winter I tried 3 months of Warner's
2 part buffer and had o.k. results (Ca 400, dKH 8.5) but needed to use
maximum amounts (estimated to cost >$300/year). I am concerned about
my calcium and alkalinity supplementation. I have noticed some bad
mouthing of the Kent products in the FAQs...any specific problems?
<Well, in most cases they are the great imitators... copied products
from other companies that did the actually research.> Will this
amount of Turbo Calcium cause an ionic imbalance and how do I recognize
the symptoms? <One or the other [ph/dKH] will be very high, much
higher than they are now.> What Ca reactor media do you like the
best? <Knop Korallith.> How would you recommend I proceed? <I
would consider two things... first, unless you've done this
already, you should replace at least half of your live rock and sand
bed. This is a process that should be done once a year in smaller
percentages, but I get the feeling you've never done this... your
alkaline reserve is really embodied in your sand bed and live rock, and
over time it gets used up. Adding supplements is only useful to the
point that they actually have a place to go. Also, if you don't run
your refugium this way, pack it with macro-algae and light it during
times when the tank is dark - this would help keep your pH a little
higher and also allow you to turn up the calcium reactor a little bit.
Do start with swapping out some rock and sand - this is the best place
to start.> Thank you for your response...you guys do a great job!
Sean <Cheers, J -- >
- Ca & Alk, Calcium Reactor - Hello again and thanks for
all the past help. My system has been running at pH 8.2, Ca 320ppm and
Alk 10-11dKH since installing calcium reactor three months ago. I have
tried to increase Ca by increasing bubble count to 120/min (started at
60) while keeping flow constant at manufacture's recommended
starting point of 2-3l/hr. Effluent is close to ph 6.5 and 40 dKH.
Trend seems to be that as I increase bubble count, alk increases but
not Ca. I understand that Ca is necessarily lower when alk is high. Is
this just a function of reactor media (ARM) and will I have to
supplement Ca or will I eventually be able to dial in Ca to 350-400ppm
with the right combination of CO2 and flow. <Well, two things come
to mind - first, the ARM media is notoriously impure, which means you
really can't rely on it for consistent results. Second, calcium
reactors are 'really' alkalinity reactors, and by boosting
alkalinity promote better availability of calcium - of course it helps
that the effluent is calcium carbonate, but really, I don't see
anything wrong with those numbers. Do also use the growth of your
calcium consuming organisms as a guide.> Perhaps I need different
media (suggestions?), <Knop Korallith.> or is 320ppm & 11dKH
just fine and I should leave it alone? <Yes to that as well.> A.
yongei frag is doing well so far but want to get everything right
before starting to stock in earnest. Regards, George. <Cheers, J --