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dKH, pH, and Calcium...still can't get it right

2656 Views 18 Replies 7 Participants Last post by  FishDaddy
Hello! (Tom, you might have just the recipe for this one...)

I apologize for the length, but the info might be necessary for the plan of correction...

First of all, I've been rereading Delbeek & Sprung Vol I and various articles Tom Wyatt's written in the posts here that I've collected and printed over time....
Over the past 6 weeks, conditions in both large tanks have improved, but I'm at a point where I'm afraid I'll run into trouble and I still can't get it right. Here are the current readings:

Tank 1:
120G Reef w/20G sump, macroalgae growing in the sump, sump light on at night. 2 175w 10,000K MH with 2 110w VHO actinics
2 Maxi 1200's, vertical spray bar down the center, horizontal spraybar across the bottom, GenX Mak4 return pump, Berlin TriplePass skimmer in sump, 4-5" sandbed w/plenum, tons of LR. 3-1/2 yrs old. 7 fish, 10 Hr photo period

Leathers are thriving and growing WELL. Frogspawn has improved tremendously in past 6 wks, added Galaxia month ago and it's thriving well. One sps "cup" is doing well - added it in early April. Can't keep other sps's healthy or alive, haven't tried more than two, lost both.

Chemistry - as of afternoon today, 5/12/02:
(All test kits are Salifert, Kent Marine 3-stage RO unit)

pH: 8.02 (never gets higher) Using calibrated Pinpoint Probe.

Nitrates: <25

Calcium: ~390 (was ~340 a month ago, used to be 475 ages ago)

ALK: 5.0 / 13.6dKH (used to be 4.34 / 12.2 fairly consistently)

SG: 1.024

PO4: 1.0; or .33 phosphate/phosphor (which is the orthophosphate reading??)

Nitrites and Ammonia: 0

I've used Kalkwasser, B-Ionics 1 & 2, and Aragomight on alternating times to try to get the calcium and pH up. I added the Maxi 1200's at opposite ends aimed at the surface to get more surface movement, and we've done 15-20 gal water changes every 2-3 weeks for the past couple of months. There is currently no significant hair algae or other algae problem.

I'm afraid I'm going to get the alkalinity up too high while trying to get the calcium up and the pH up some.

Our auto-topoff water has always just been RO water, nothing added. I'm thinking I should add Kalkwater to the topoff? Can I add aragomight at the same time, or just one product at a time? I've been adding 35cc's B-Ionic 1 & 2 each after the lights go out or first thing in the morning.

The 125G FOWLR tank (>2 yrs old) has the same sand/plenum/return-pump/sump/skimmer/pwrhead specs, with PC smartlight lighting and auto-topoff, RO water w/nothing added,
7 fish, and here's its chemistry:

Calcium: 500+ (!)

pH: 7.82 (up from 7.6-7.7 a couple months ago)

ALK: 3.7-meq/l / 10.4-dKH

Nitrates: 100 (!) (down from 100+, and feeding MUCH LESS!)
also, never have had an algae problem in this tank...

PO4: slightly >1.0

Nitrites and Ammonia: 0

SG: 1.024

I only add the B-ionics to this tank now since the calcium jumped up so high. (35cc ea every day or every other day)

Have done 15-20 gal water changes every two weeks for past couple months and added plants to the sump today.

Now what?

Thanks VERY MUCH in advance!
Shirley :) :confused: :)
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Try dosing some Magnesium by SeaChem. It works in cahoots with the Calcium in the tank. I'm sure Tom or Jerel could explain. I'd give that a try first. If that doesn't work, you might try a little bit of Kent's turbo calcium. The whole alk/ca/pH thing is definately one of the harder things to understand in a tank. You want to buffer to get the pH up, then you alk shoots way up and depletes your calcium level.

Still confused too :rolleyes:

Ditto on Brooke's post on the Mag. same thing happened to me a while back, never could get the Calc back up to levels, tried a dose of the magnesium from Kent,,,,got better right away!i have since put a bit in every week , calc has stayed at 450 no problem!
(Jason at Premium oughta have it)

Hope to get down there to see you and the tanks ,Shirl.
promise to bring down some goodies too!:)

oops, forgot,,,,,like Brooke said, get some Kent's turbo-calc too! you'd be glad you did:)
Thanks Brooke and Jeff,
I appreciate your replies! I also finally got through to my son, Troy (brilliant in chemistry).
He immediately said I needed to add Calcium Chloride, which is what Turbo-Calc is (I read the label to him on the PA store site). He explained that Calcium Chloride raises calcium but does not affect buffer or pH (is not affected by buffer, also, I think he said) and would not raise alkalinity. He went on and on about an-ions and cations (cat-ions) and all sorts of things Tom Wyatt would understand, and turns out all the calcium I have is calcium carbonate or calcium hydroxide and I needed calcium chloride, such as you both recommended.

I will get some Kent's Turbo-Calc and use it in the 120G.

Now, how do I raise pH without further raising dKH??

And how do I raise pH in the 120 and not raise the calcium levels any higher?

Should I get Magnesium and Strontium to add as well? Troy agreed with you, Brooke, on the Magnesium. I thought it was in the CombiSan, but when I read out all the chem letters it turns out it has Manganese, but not Magnesium.

THANKS! I'll keep reading, keep looking for answers, and I'll get the Turbo-Calc as soon as I can get to PA and I'll let you know...

Shirley :)
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ShirleyM said:
Chemistry - as of afternoon today, 5/12/02:
(All test kits are Salifert, Kent Marine 3-stage RO unit)
pH: 8.02 (never gets higher) Using calibrated Pinpoint Probe.
Nitrates: <25
Calcium: ~390 (was ~340 a month ago, used to be 475 ages ago)
ALK: 5.0 / 13.6dKH (used to be 4.34 / 12.2 fairly consistently)
SG: 1.024
PO4: 1.0; or .33 phosphate/phosphor (which is the orthophosphate reading??)
There is good info on the suggestions so far, although I would test your Magnesium and look at the level in perspective with your SG in terms of the Chlorality of the seawater column before making adjustments (If you don't know about this, I will post it later). Several observations about this set of parameters.

Let me lead off by saying that your parameters are not bad. If you look at the composition of 1 kg of seawater with a Cl = 19.374, the amount in GMs of the major components is:

  • Na+ ................10.7822 gm
    Mg++...............1.2837 gm
    Ca++...............0.4121 gm
    K+...................0.3991 gm
    Sr++................0.0079 gm

    Cl- ..................19.3529 gm
    SO4--...............2.7124 gm
    HCO3-..............0.1135 gm (can vary with alk level in aquaria)
    Br-...................0.0672 gm
    CO3-................0.0116 gm (can vary with alk level in aquaria)
    B(OH)4-............0.0013 gm*
    B(OH)3.............0.0203 gm
    (* borate exists as both ionized and unionized in seawater)

In this example your Calcium is a little down, but not completely out of the picture, as well as your alkalinity. Many hobbyists shoot for the holy grail of 450 PPM and up with alkalinities of 13 to 15 dKh, but in reality, these levels do not reflect the levels of NSW and are not necessary to keep Acroporoids and other stony corals alive and thriving. With that said, I admit to shooting for over 400 PPM Ca and 12 dKh or so for Alkalinity, as these seem to be the best levels for maintaining stony coral growth. Many experienced long term captive coral cultivators report that alk in the ranges below 11 to 12 and above 13 seem to be less than optimal for stony coral growth. Similar reports are available for Ca levels much above 425 or below 375 PPM. Aiming for levels much above these levels is both time consuming, wasteful, and without need, as the "more is better" concept does not necessarily apply under these circumstances, and does not reflect the natural levels of these substances in the ocean's water column in reef biotopes. (See Sorokin, Tomascik, and Millero references for the data).

As to your particular situation, high nitrates will aid in the solubilization of Calcium. Think of a stadium (your aquarium) where there are only so many seats available (the anion species in the water column, the items in the list above with minus signs). By having more nitrates in the water column, there will be more seats in the stadium for attendees to sit in (the cations, or substances with plusses after them in the list above). Some attendees can only sit in certain seats, (maybe they have very large hip measurements!) others will sit wherever they can. Calcium as a cation can only pair up with so many seats, and some other cations will rush to sit in seats before Calcium can find a seat that is capable of allowing the calcium to sit down. Extra Nitrates in the water column allows for more Calcium to sit in the stands. Although some calcium will be allowed to stand in the isles, for the most part, the stadium police (parameters of solubility) will make Calcium leave the stands, where the Calcium cannot participate in any activities going on in the stands (it precipitates out of solution). When the Calcium is out of the stadium (precipitated), it cannot be counted as an attendee of the stadium, neither can it participate in "the wave" or any other stadium activities with the other fans. This happens when excessive phosphate ions are in solution. In our analogy, phosphate could be thought of as season box holders. There are only so many spaces in a particular sized stadium that are the reserved box seats, and only so many that can be built as well (or the regular fans would revolt!). If Phosphate were thought of as box holders that bring in folding chairs, only so many folding chairs can be brought into the season boxes, so that when more are brought in, even if Calcium were to sit in them, the Stadium ticket police would make them leave the stadium (or precipitate out of solution, and cannot participate in stadium activities). All the phosphate chairs preferentially fit Calcium requirements, so for every extra folding chair that phosphate brings into the stadium (in our aquaria, this is from feeding source phosphate, water from the tap or exhausted RO/DI filters, etc.) Calcium tries to sit in it, and if the season boxes are full and Calcium sits in an isle with a phosphate chair, Calcium is made to leave the stadium, reducing the number of Calcium fans (cations) in the stadium taking the chair with it.

Conversely, adding extra Calcium fans into the stadium when there are large numbers of Phosphate folding chairs will also reduce the number of chairs in the stands as Calcium fans are escorted from the stadium (thus reducing phosphate in the water column.) This is what happens when introducing Kalkwasser to reduce phosphate levels as well.

I suspect that in this example, your aquarium probable has excess nitrate solubilizing the Calcium that is there, allowing your calcium levels to climb above normal. Reducing your nitrate will prolly reduce your Ca levels as well. Introducing a reverse photoperiod refugium with Caulerpa growths will help to export your nitrate by harvesting the macroalgae that you will grow there. If you do not have this already, adding sugar-sized sand (preferably aragonite) will develop a DSB that will reduce your nitrates to below 10 PPM. Add the sand either to the display (preferably) or to a large refugium/sump.

If this was not problematic enough already, pH plays a role in both the levels of alkalinity and the solubility of Calcium, and is driven by the concentration of Carbon Dioxide (CO2) in the water column. Salinity plays a role as well, controlling the levels of the solutes as well as controlling the actual numbers of "seats" and "occupants" in the stadium, and just how strictly the "Stadium Police" regulations will be adhered to.

As it is 2am here, I will stop for tonite. Please post questions about the analogy so far (for those of you familiar with the concepts of the carbonate/bicarbonate buffer system and it's relationships with Ca and pH, I readily admit I have taken a few liberties here, but this analogy will do to explain the concepts of the systems). Shirley, for Drew's benefit, I have possibly oversimplified these concepts, but I think it will make it easier for those that don't have some chemistry or at least a general science background to understand as well. Heck, I used my attorney brother as a guinea pig for this analogy/concept, and he understands it now...:rolleyes:
example:what is the difference between a catfish and an attorney?

Hope this helps, it is a very easy concept to understand once you are familiar with the ground rules.
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Thanks so much, Tom, you are an AWESOME teacher!!

I learn best with analogies, models, and drawings, and your analogies were just terrific and so clear, not to mention amusing.
I printed your post early this a.m. and read it - slowly - during the 50 min drive to's still sinking in, and I'm trying to not let any of it precipitate out! ;) I'll read it again when I get home this evening.

Anyway, I'm stopping at PA on the way home and picking up a Magnesium test kit, Kent magnesium additive, Kent turbo-calc (I'll be careful with it) and I'm also replacing our RIO pumps with Mag5 and Sen700 to run the two skimmers (that's a side note)
We're also getting a PA refractometer on SALE there so I know the exact SG readings. Ours is off when compared to good ones.

I want desperately to get this running like it used to and keep it running well....


your SG in terms of the Chlorality of the seawater column before making adjustments (If you don't know about this, I will post it later).
No, I don't know what you mean about "chlorality of the seawater"...

Another Question: When this is all straightened out, is it ever OK or good practice to keep sps corals with soft corals? They (sps) used to live and grow fairly well... Of course, the leathers have grown much larger since then...

Last question: Should Kalk water make up the topoff water? We keep it (RO) in a covered Rubbermaid tub, holds about 13 gallons, lasts about a week or less. If it's made up of Kalk water, then do I dose the B-ionics about 1/2 strength daily? THANKS!

I can't thank you all enough!! I'll let you know the magnesium levels when I do the test tonight.

Shirley :)
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tested Magnesium

Hello Brooke, Jeff, and Tom,

I just tested the Magnesium in both tanks and it IS low...

120G reef: 1180 ppm

125G FOWLR: 1250 ppm

According to Salifert kit, supposed to be: 1300-1500 ppm

So, I will add the Kent Marine Magnesium per instructions of one ml per gal daily until corrected? That's 120 ml (cc's)! Seems like a lot...I will do 1/2 that and wait to get further advice...

I also got a refractometer at PA on the way home. SG is 1.0240 in both tanks (my $10 swing arm claims 1.0225, and I knew it measured low)

Do I need to be testing for Strontium?? (these test kits are expensive!)

Now I'll study the directions on the Turbo Calcium...

Thanks again,
Shirley :)
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Good morning!

A couple more questions: You recommended the sugar-sized sand added to the DSB...add it on top covering all the existing surface? 1/2"? 1"? +/-? I happen to have enough of that for a 4" coverage in a 10G tank, used but clean and sitting in a bucket. With a plenum, is it still recommended? (it's so milky when stirred up...)

Also, Tom, what is "Cl" and "GM" in your sentence "1 kg of seawater with a Cl=19.374, the amount of GMs of the major component is...

Shirley :)
Hi, I was under the impression that calcium chloride would affect alkalinity, driving it down. This is further noted by the fact that most reef calcium additives are 2 part one for raising Dkh and one for calcium.

I'm also confused somewhat by this stuff, but learning. :)
Tom, my hat's off to you. Not only was that the best explanation I've ever ever heard, it's in a way that you'll remember it.
Kudos kudos me amigo!

Shirley, I'm willing to bet when you beef up those skimmers you'll see a big difference in Ph too.
ShirleyM said:
what is "Cl" and "GM" in your sentence "1 kg of seawater with a Cl=19.374, the amount of GMs of the major component is...
Hey Shirley, sorry I haven't posted the responses to this, I have 2 more 12 hour days of patients, then a day off and my oldest son Gets married this weekend, heh! I promise to try and post before the week is over on part 2 and the many q's for this subject, but I will give you a little that may save you a headache or two before you add the magnesium. You said your magnesium is a little low. I looked at the numbers and they are low if you compare your numbers TO FULL STRENGTH SEAWATER. As your SG is low, think about what seawater is, and how we measure what the seawater is composed of. Full strength seawater is around 35 PPT dissolved salts. This gives a SG at tank temps of around 1.026. Your SG was low, around 1.022, I think you said... Just in terms of this, your SG is around 15% off of the actual value you should have for your salinity (Actually a lot for a reef aquaria). This means that the conservative elements for the water column will be around 15% less than they would be if the values were brought up to NSW values. We always want to adjust the amounts of conservative elements to the correct values in the proportion to each of the other conservative elements in seawater, regardless of the strength/salinity of that seawater . In measuring seawater values over the surface of the earth (deep water chemistry is a bit different, let's agree not to discuss that now, as it has little significance to our current discussion), all the values of the conservative elements are in the same proportion to each other, regardless of the salinity of that water. Red sea salinities are up to 40 PPT, the mid Atlantic at 37 PPT, Indonesian Seas 35 to 36 PPT depending on how close the locations are to large land masses. In all these varied locations, the salinity may differ, and the actual amounts of the conservative elements may be greater or less in their respective locations per liter of seawater, but the ratios of each element remains constant. One of the ways we standardize all these measurements, regardless of the changes associated with salinities and SG's and temp of the water and pressure associated with depth is to measure the amount of Chloride/chlorine in a sample. This may be done with a special electrode, or using the silver nitrate method, and gives the true measure of Chloride in a volumetric standard. This is termed the Chlorinity of the sample, and all other conservative elements can be extrapolated from that value in the tested sample. (Edit note: Chlorality was a mini-stroke I had during the nite when I wrote the initial response to the thread, I apologize for the error, heh, too many late nites and long days...--tdw). Based on studies through the years and or corrections as the Table of Elements has been corrected (atomic weights), the following is a table of the relative composition of the major (conservative) elements of Seawater:

  • *****************indexed Gm/Cl (o/oo)*********

    Cl-................0.99894....(both assumed 1.00)....0.99891

A: Dittmar as recalculated by Lyman and Fleming (J. Mar. Res., 3, 134, 1940)
B: Cox and Culkin (Deep Sea Res., 13, 789, 1966)
C: Riley and Tongadai (Chemical Geol., 2, 263, 1967): Morris and Riley (Deep Sea Res., 13, 699, 1966)
D: Millero (Ocean Sci., 7, 403, 1982)

That the chart above does is give us values for an ion based on it's relationship to the amount of chlorine in a sample. For example, if we tested a sample of seawater and found it's chlorinity to be 19.374 (Cl=19.374, that of Normal SeaWater (NSW)) Then using the above table we can calculate it's sodium content in a liter:
  • 19.37 x 0.5556 = 10.76gms of Sodium/liter.
Likewise, if we know the salinity of the solution (NSW, we can calculate what our Magnesium should be in relation to the strength of the solution. Knowing our salinity was of SG 1.022, this is approximately 15% lower than our standard should be. if our NSW Magnesium should be 1.2837 gm/liter (using the table), then 15% less total dissolved salts would result in a concentration of 15% less Magnesium, or a value of 1.091 g, = 1091 or approx. 1100mg/l, which corresponds with your Mg level. To restore your Mg, you would only need to gradually bring up your salinity to 35 ppt (SG 1.026) over 3 to 5 days by adding fresh seawater for top off instead of RO water and testing your SG after an hour of circulation. This will also bring up your effective alkalinity, and by supplementing both Ca and Alk with Bionic at 40 ml each of part A and Part B, your Ca should be in the 400 to 425 PPM range, and your alk should come up to 12 or 13 dKh after a week of daily supplements. 10% water changes will help to restore your conservative rations over time. Stick with good husbandry practices and I suspect that as your SG comes up, your tank will return to it's normal healthy self.

Sorry to go so long, I will post another installment on the stadium analogy and Calcium sinking in the biogenesis of reef strata before the week is out.

By the way, Thanks Jerel for the comment! Heh, Made that one up myself!!!

Hope this helps.
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Jimbo said:
Hi, I was under the impression that calcium chloride would affect alkalinity, driving it down...
Hey Jim,
actually, CaCl2 would drive pH down, but only very temporarily, and only a small bit even then. The Chloride is taken up quickly by sodium, potassium, magnesium, etc. without the net release of protons (H+) as the Calcium preferentially associates with Carbonate/bicarbonate without seeing shifts in pH or a net release of protons as well. The Calcium Carbonate that is formed is part of the equilibrium for the buffer system, and actually helps resist changes in pH, although when exceeding concentrations much above the 350 range(PPM) ionized caCO3 begins to associate and precipitate out of solution. This too, adds to the equilibrium, as it saturates the solution (usually supersaturated in aquaria due to Mg salts) and acts as a reserve (although slow to react) for the buffer system. I will post more on this on the weekend. Feel free to post any q's, I will prolly not be online untill late Thursday nite.

Hope this helps.
Well Heck!!!

...and I thought I was chumming the waters... is a slime-covered, detritus consuming, scum-sucking bottom feeder...

...the other is a fish... :D
5/16 Update

Hello Tom,

Thanks again so much for your posts!

I had already added 1/2 dose Mg 3 times (p.m., a.m., p.m.) when I rec'd your post. I didn't add any yesterday or today, but I upped the Salinity a little. It's 1.025 now. It was 1.024 before, not 1.022. My cheap tester was not accurate and I got a PA Refractometer on sale Monday. This info is for both reef and fowlr tanks.

120G Reef tank; Tonight, 5/16/02:
pH day: 8.26, night: 8.03

Calcium: was up to 405 Weds, now it's 390. I had added the Calcium Chloride (Kent's Turbo Calc) twice since Monday. Didn't add any yesterday.

Magnesium: before adding anything - 1180.
Mg Tuesday: 1215
Today (Weds): 1230

Question: Should I add anything to the topoff water? If so, decanted Kalk? Aragomight?

Shirley :)
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Re: 5/16 Update

ShirleyM said:
...Calcium: was up to 405 Weds, now it's 390. I had added the Calcium Chloride (Kent's Turbo Calc) twice since Monday. Didn't add any yesterday.
before adding anything - 1180.
Mg Tuesday:.................. 1215
Today (Weds): .............. 1230
Question: Should I add anything to the topoff water? If so, decanted Kalk? Aragomight?
Hey Shirley, I will post more on the Ca analogy later this weekend when things slow down, It's been hectic with the wedding going off tomorrow (Heh! Talk about expensive habits, just take 40 folks to the rehersal dinner in a nice restaurant and pay for wine and a live jazz band... Sheesh!:eek: )

I don't know what your normal routine is, but you definitely need to be supplementing on a daily basis with some sourc3 of calcium. What do you do now to supplement? I thought you were already adding a supplement to your system. Dripping in Kalk for all of your replacement would be almost a given for your reef system, just make it fresh every day and replace all your evaporation over 4 to 6 hours with a slow drip. I will be glad to show you some quick tricks for doing this, but they will require that you know your evap rate within 100 to 200 ml/day.

Stop the Mg supplements for now, work on 10% to 20 % changes once a week for a while. Lemmeno what you're doing for routine Ca++ and alkalinity supplementation.

More later...
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Originally posted by ShirleyM
pH: 8.02 (never gets higher) Using calibrated Pinpoint Probe.

getting ready to work on the post tomorrow, but wanted to ask if you have ever cleaned the end of the Pinpoint probe with a soft toothbrush, At times buildup occurs on the probe and will skew your responses.

Catching up, I may post a few pix of the wedding on the home page, it was a blast, but I have to say, I'm glad its done.
Hey Tom!
Congratulations on the wedding! (Did they have a videographer? ;) )

No, I haven't cleaned the probe, nor did I know I could. Will do that this evening...

I did set up a Kalk drip with a doser we had. The new Mag 7 (that replaced the Rio 2500 on the skimmer) worked overtime and caused a 15 gallon overflow Sat. morning...GenX Mak 4 return pump ran dry but still works fine, thank heavens! The Mag 7 is adjusted and working fine now, salt is back at 1.025, and pH was at 8.2 yesterday afternoon. Kalk drip was started yesterday morning.

I'd always added the kalk or aragamite or B-ionics manually beofre; this Aqua-doser was in a box of misc. that came with the used 125G 2 yrs ago and quite honestly I'd forgotten we even had it! Found a new Mag 2 in that box, too!

Plain RO water is in the topoff tub, nothing added to it.

Have a GREAT day!
Thanks for everything!
Anxious to see your pictures!
Shirley :)
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Great stuff....Thanks, TD.
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