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FAQs on Calcium and Alkalinity in Seawater, Sources 

Related Articles: Calcium and Alkalinity Explained by Anthony Calfo, Calcium, Biominerals, The Use of Kalkwasser by Russell Schultz, Calcium Reactors, Marine Maintenance, Marine Water Quality, Magnesium in Seawater, Strontium in Seawater, pH, Alkalinity, Marine AlkalinityLive Sand, Marine SubstratesReef Systems, Refugiums

Related FAQs: Ca/Alk 1, Ca/Alk 2, Ca/Alk 3, & FAQs on: The Science of Calcium & Alkalinity, Importance, Measure, Use of AdditivesTroubleshooting/Fixing, Products, & Calcium, & FAQs on Calcium: Rationale/Use, Calcium Measuring/Test Kits, Sources of Calcium, Calcium Supplements, Dosing, Chemical/Physical Interactions, Troubleshooting/Fixing, & Calcium Reactors, & 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 Marine Supplements 1,

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     7/25/16
Hi all
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, organisms....>
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 corals.
<.... 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>
Thanks muchly
<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 live rock.>
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 ½ 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 ½ 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 stony corals.>
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 without it.
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 thoughts?
<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
<Hello Sarah>
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 alone.>
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 home.
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 time?
<Yes, is the safe way to do this although acid buffers will lower the dKH, and I would advise against
doing this.>
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

Back again.
<Hi Sarah>
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. UGH!>
Anyway, looking at the Tropic Marin Alca Balance. It is hard to find.
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 level?
<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 them.>
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 aquariums?
<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 here.
"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!
Best regards,
Lou Ekus
Director of US Operations
Tropic Marin"
<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, Gage>

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 -- >

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