How high is too high?

Rovert

Active Member
Review score
+0 /0 /-0
View Badges
Joined
Jun 14, 2022
Messages
196
Reaction score
139
Review score
+0 /0 /-0
Location
Milford, PA
Just added a couple Maximas to the tank and will be watching Alk/Ca/Mg, but wondering how high approaches a danger zone. My Alk has been as high as 12.3 dKH, Ca about 450-ish this past week until I stopped the CO2 to the reactor and let it settle back to high 10's for the moment. My plan is to use my Trident to cycle the Co2 on and off to maintain a reasonably stable range. Many recommendations of only 8 dKH seem low to me for an SPS dominated tank. Opinions on what to shoot for?
 
Tidal Gardens

Tonycass12

Well-Known Member
Review score
+0 /0 /-0
View Badges
Joined
Nov 18, 2020
Messages
913
Reaction score
1,485
Review score
+0 /0 /-0
Location
Traverse city
8dkh is more along the lines of what I see in many successful sps dominant displays. Much easier to care for as well with some wiggle room before anything gets upset. IMO its easy to upset corals when dkh is as high as your running it.
 
Never Wash Another Nasty Filter Sock Again!

vetteguy53081

Well known Member and monster tank lover
Review score
+5 /0 /-0
View Badges
Joined
Aug 11, 2013
Messages
68,809
Reaction score
148,644
Review score
+5 /0 /-0
Location
Wisconsin - Florida delayed due 2 hurricane damage
Just added a couple Maximas to the tank and will be watching Alk/Ca/Mg, but wondering how high approaches a danger zone. My Alk has been as high as 12.3 dKH, Ca about 450-ish this past week until I stopped the CO2 to the reactor and let it settle back to high 10's for the moment. My plan is to use my Trident to cycle the Co2 on and off to maintain a reasonably stable range. Many recommendations of only 8 dKH seem low to me for an SPS dominated tank. Opinions on what to shoot for?
Everyone will have their own and favorite range but the industry recommendation is generally

Alk no higher than 11
CA no higher than 450
Mag no higher than 1350

These would be ranges and not tartgets
 

landlubber

Valuable Member
Review score
+0 /0 /-0
View Badges
Joined
Mar 20, 2017
Messages
1,176
Reaction score
1,045
Review score
+0 /0 /-0
Just added a couple Maximas to the tank and will be watching Alk/Ca/Mg, but wondering how high approaches a danger zone. My Alk has been as high as 12.3 dKH, Ca about 450-ish this past week until I stopped the CO2 to the reactor and let it settle back to high 10's for the moment. My plan is to use my Trident to cycle the Co2 on and off to maintain a reasonably stable range. Many recommendations of only 8 dKH seem low to me for an SPS dominated tank. Opinions on what to shoot for?
Your Ca values are really no concern and can be changed without incident but would be very cautious bringing that dkh down and would make a plan over the next several months to bring it down in very minor increments.
 
World Wide Corals

Randy Holmes-Farley

Reef Chemist
Review score
+0 /0 /-0
View Badges
Joined
Sep 5, 2014
Messages
54,595
Reaction score
47,402
Review score
+0 /0 /-0
Location
Arlington, Massachusetts, United States

Randy Holmes-Farley

Reef Chemist
Review score
+0 /0 /-0
View Badges
Joined
Sep 5, 2014
Messages
54,595
Reaction score
47,402
Review score
+0 /0 /-0
Location
Arlington, Massachusetts, United States
Just added a couple Maximas to the tank and will be watching Alk/Ca/Mg, but wondering how high approaches a danger zone. My Alk has been as high as 12.3 dKH, Ca about 450-ish this past week until I stopped the CO2 to the reactor and let it settle back to high 10's for the moment. My plan is to use my Trident to cycle the Co2 on and off to maintain a reasonably stable range. Many recommendations of only 8 dKH seem low to me for an SPS dominated tank. Opinions on what to shoot for?

Here's my generic alk recommendation:

Alkalinity

Like calcium, many corals also use "alkalinity" to form their skeletons, which are composed primarily of calcium carbonate. It is generally believed that corals take up bicarbonate, convert it into carbonate, and then use that carbonate to form calcium carbonate skeletons. That conversion process is shown as:

HCO3- → CO3-- + H+

Bicarbonate → Carbonate + proton (which is released from the coral)

To ensure that corals have an adequate supply of bicarbonate for calcification, aquarists could just measure bicarbonate directly. Designing a test kit for bicarbonate, however, is somewhat more complicated than for alkalinity. Consequently, the use of alkalinity as a surrogate measure for bicarbonate is deeply entrenched in the reef aquarium hobby.

So, what is alkalinity? Alkalinity in a marine aquarium is simply a measure of the amount of acid (H+) required to reduce the pH to about 4.5, where all bicarbonate is converted into carbonic acid as follows:

HCO3- + H+ → H2CO3

The amount of acid needed is equal to the amount of bicarbonate present, so when performing an alkalinity titration with a test kit, you are counting the number of bicarbonate ions present. It is not, however, quite that simple since some other ions also take up acid during the titration. Both borate and carbonate also contribute to the measurement of alkalinity, but the bicarbonate dominates these other ions since they are generally lower in concentration than bicarbonate. So knowing the total alkalinity is akin to, but not exactly the same as, knowing how much bicarbonate is available to corals. In any case, total alkalinity is the standard that aquarists use for this purpose.

Unlike the calcium concentration, it is widely believed that certain organisms calcify more quickly at alkalinity levels higher than those in normal seawater. This result has also been demonstrated in the scientific literature, which has shown that adding bicarbonate to seawater increases the rate of calcification in some corals. Uptake of bicarbonate can consequently become rate limiting in many corals. This may be partly due to the fact that the external bicarbonate concentration is not large to begin with (relative to, for example, the calcium concentration, which is effectively about 5 times higher).

For these reasons, alkalinity maintenance is a critical aspect of coral reef aquarium husbandry. In the absence of supplementation, alkalinity will rapidly drop as corals use up much of what is present in seawater. Water changes are not usually sufficient to maintain alkalinity unless there is very little calcification taking place. Most reef aquarists try to maintain alkalinity at levels at or slightly above those of normal seawater, although exactly what levels different aquarists target depends a bit on the goals of their aquaria.

Interestingly, because some corals may calcify faster at higher alkalinity levels, and because the abiotic (nonbiological) precipitation of calcium carbonate on heaters and pumps also rises as alkalinity rises, the demand for alkalinity (and calcium) rises as the alkalinity rises. So an aquarist generally must dose more calcium and alkalinity EVERY DAY to maintain a higher alkalinity (say, 11 dKH) than to maintain 7 dKH. It is not just a one-time boost that is needed to make up that difference. In fact, calcification gets so slow as the alkalinity drops below 6 dKH that reef aquaria rarely get much below that point, even with no dosing: natural calcification has nearly stopped at that level.

In general, I suggest that aquarists maintain alkalinity between about 7-11 dKH (2.5 and 4 meq/L; 125-200 ppm CaCO3 equivalents). Many aquarists growing SPS corals and using Ultra Low Nutrient Systems (ULNS) have found that the corals suffer from burnt tips if the alkalinity is too high or changes too much. It is not at all clear why this is the case, but such aquaria are better served by alkalinity in the 7-8 dKH range.
As mentioned above, alkalinity levels above those in natural seawater increase the abiotic precipitation of calcium carbonate on warm objects such as heaters and pump impellers, or sometimes even in sand beds. This precipitation not only wastes calcium and alkalinity that aquarists are carefully adding, but it also increases equipment maintenance requirements and can damage a sand bed, hardening it into a chunk of limestone. When elevated alkalinity is driving this precipitation, it can also depress the calcium level. An excessively high alkalinity level can therefore create undesirable consequences.

I suggest that aquarists use a balanced calcium and alkalinity additive system of some sort for routine maintenance. The most popular of these balanced methods include limewater (kalkwasser), calcium carbonate/carbon dioxide reactors, and the two-part/three part additive systems.

For rapid alkalinity corrections, aquarists can simply use baking soda (sodium bicarbonate) or washing soda (sodium carbonate; baked baking soda) to good effect. The latter raises pH as well as alkalinity while the former has a very small pH lowering effect. Mixtures can also be used, and are what many hobby chemical supply companies sell as “buffersâ€. Most often, sodium carbonate is preferred, however, since most tanks can be helped by a pH boost.
 

I never finish anythi

Active Member
Review score
+0 /0 /-0
View Badges
Joined
Aug 11, 2022
Messages
141
Reaction score
80
Review score
+0 /0 /-0
Location
Wales
You maintain 20 dKH in a reef tank? How? That would seem unstable to me. Is the pH on the low end?
No I messed up with all for reef , my red sea test kit is saying 7.5 dkh , but my salifert is telling me 20 dkh . Not good . It's still on 15.5 yikes . I want it 8.5
 
AquaCave Logo Banner

TokenReefer

Well-Known Member
Review score
+0 /0 /-0
View Badges
Joined
Oct 4, 2022
Messages
642
Reaction score
741
Review score
+0 /0 /-0
Location
CT
No I messed up with all for reef , my red sea test kit is saying 7.5 dkh , but my salifert is telling me 20 dkh . Not good . It's still on 15.5 yikes . I want it 8.5
Out of curiosity what's your ph at that level dkh? Just trying to understand PH relationship a bit better... if you don't mind me asking
 

I never finish anythi

Active Member
Review score
+0 /0 /-0
View Badges
Joined
Aug 11, 2022
Messages
141
Reaction score
80
Review score
+0 /0 /-0
Location
Wales
Out of curiosity what's your ph at that level dkh? Just trying to understand PH relationship a bit better... if you don't mind me asking
Dkh 15,5 salifert. Red sea is saying 8.4 on the ph saying that maybe 8.6 not the best to test with tho . Corals seem ok and the inverts .
 
www.dinkinsaquaticgardens.com
Tenecor AIO Conversion Kits Now Available!

Randy Holmes-Farley

Reef Chemist
Review score
+0 /0 /-0
View Badges
Joined
Sep 5, 2014
Messages
54,595
Reaction score
47,402
Review score
+0 /0 /-0
Location
Arlington, Massachusetts, United States
Wow that's surprising to me; I was expecting higher. I wonder if your base water (rodi?) is low PH.... Do you trust your alk test?

RO/DI pH has no impact on seawater pH made from it. In fact, adding totally pure water at pH 7 to seawater at pH 8.1 raises the pH.

All other things equal (that is, equilibrated with the same air) doubling the alk will raise the pH by about 0.3 pH units.
 

TokenReefer

Well-Known Member
Review score
+0 /0 /-0
View Badges
Joined
Oct 4, 2022
Messages
642
Reaction score
741
Review score
+0 /0 /-0
Location
CT
adding totally pure water at pH 7 to seawater at pH 8.1 raises the pH.
Really?! Does that depend on a certain level of alkalinity?

I'm going to dive in a little more just seems like every time I think I understand the basics...I'm apparently not. There's a ton that's over my head, just trying to get to a good base layman's understanding :). Thanks
 
Join the movement!

Randy Holmes-Farley

Reef Chemist
Review score
+0 /0 /-0
View Badges
Joined
Sep 5, 2014
Messages
54,595
Reaction score
47,402
Review score
+0 /0 /-0
Location
Arlington, Massachusetts, United States
Really?! Does that depend on a certain level of alkalinity?

I'm going to dive in a little more just seems like every time I think I understand the basics...I'm apparently not. There's a ton that's over my head, just trying to get to a good base layman's understanding :). Thanks

Nope, it happens because the acidity of bicarbonate depends on the salinity. It is a very sophisticated effect that I expect most reefers are not aware of unless they read the thread below.

This thread has all the details:

 

Have you bred fish in your tanks?

  • I have bred saltwater fish

    Votes: 37 13.5%
  • I have bred freshwater fish

    Votes: 119 43.3%
  • Not yet, but I am interested in breeding fish

    Votes: 64 23.3%
  • I think it is an interesting idea, but not my thing

    Votes: 62 22.5%
  • I am not interested in breeding fish

    Votes: 42 15.3%
Top