Why is lower alkalinity preferred?

[Sisterlimonpot]

Been looking into salt, I keep reading lower alkalinity is preferred in a salt, can someone please explain why this is the case? as I thought corals used alkalinity so the more the better?

I read through this thread and there is plenty of great information. But i think the underlying question hasn't been answered as to why people prefer salt mix with lower alk vs one with high alk.

It all comes down to how you conduct waterchanges. Most people go the traditional route and replace 10-20% every 1-2 weeks. And if you're using salt with 11dkh and your tank is stable at 8dkh, that waterchange is going to raise your parameters rather quickly and possibly stress the corals.

That's part of the reason people suggest finding a salt that matches your tank parameters.

Although for those that are doing 24/7 auto water changes with pumps like the versa then it doesn't matter the alk of the new salt because you're injecting it at a regular interval that isn't going to cause a large alk swings and eventually will be factored into your 2 part dosing or calcium reactor settings.

 

[EMeyer]

I get what you are saying but if the ocean is at 7, wouldn’t that be 7 net alkalinity, a tank starting at 7, then add corals it wouldn’t stay 7 for long...that’s my confusion.

I’m trying to decide between the TM classic and pro, one is 9 and the other 7, not sure if I’m any nearer deciding, thought I was nearly there!

Regardless what your target level is, if your corals are consuming alkalinity, you'll need to dose to maintain it.

Water changes will disrupt your target alkalinity if your freshly mixed SW is different from your target. Most mixes come out unnaturally high, so many of us adjust the alkalinity of the new SW prior to doing the water change.

Hobbyists differ in their choice of target alkalinity level (I still think 7 is best!) but I think most would agree that dosing multiple times per day with very small amounts, and doing water changes with water that matches your target alkalinity, are good ways to to maintain stable alkalinity.

 

[RMS18]

Ok here is where I’m at, I now get it’s easier to start low and dose if needed, I guess people dose the amount the corals use on a daily basis, not so easy to remove if you start with a level too high.
I am going for an LPS reef but if I go for the classic at 9, how do I keep the alk stable? If the corals don’t use much alk, wouldn’t water changes result in big swings? Hope that makes sense.

So let's say your tank is at 7dkh. Over the next 2 days or so you will test daily if you see alk drops to 6.5 on day 2. You know you drop .25ppm per day. Let's says 5ml of alk will increase your dkh in your tank by .25pm. now you know to keep levels stable you need to dose .25ppm per day.

Let's say your salt water mixes at 7dkh, you can do a 100% water change and as long as new sw matches tank your good.

Same process for calcium and magnesium.

 

[RMS18]

I was going with TM Pro, until I considered this exact dilemma. That’s when I settled on using HW Marine salt. Along with TM, they are also the two brands known to use pharma grade ingredients. I used HW with my very first marine tank many moons ago as well. Both their Reefer & Pro grades run about 9 dKh, which is where I’d like the chemistry to be.

HW was the salt I used or to TM. I changes for 2 reason, TM has ocean levels of all trace elements, HW does not have them all. Second HW left a brownish slime residue on my mixing container and pump/heater wires. Other than that the salt was great. TM mixes clean with no residue, mixes faster and has all the trace elements. I did a ICP on both tests and HW was missing some of levels were low.

We all know that all major salt brands can grow and keep corals. None of them wm harm your corals, at that point it's personal preference or peace of mind for a highlight that may not matter at all.

 

[ichthyoid]

I read through this thread and there is plenty of great information. But i think the underlying question hasn't been answered as to why people prefer salt mix with lower alk vs one with high alk.

It all comes down to how you conduct waterchanges. Most people go the traditional route and replace 10-20% every 1-2 weeks. And if you're using salt with 11dkh and your tank is stable at 8dkh, that waterchange is going to raise your parameters rather quickly and possibly stress the corals.

That's part of the reason people suggest finding a salt that matches your tank parameters.

Although for those that are doing 24/7 auto water changes with pumps like the versa then it doesn't matter the alk of the new salt because you're injecting it at a regular interval that isn't going to cause a large alk swings and eventually will be factored into your 2 part dosing or calcium reactor settings.

I’m striving for overall health, stability & convenience. So use a salt with close to my target parameters the HW Marine, with continuous water change & dose All for Reef via Apex using the target alk of 9 dKh to gauge the rate. I aim for zero swings.

Instructions:

Start with a daily dose of 5 ml of All-For-Reef per 100 liters (26 US-gal) of aquarium system volume. Increase the daily dosage – by continuous control of the alkalinity – weekly by 2.5 ml per 100 liters (26 US-gal) of aquarium system volume, until a constant carbonate hardness of 7 to 9 °dH is reached.

 

[Potatohead]

If you are going to keep stony corals, at some point you're going to need to dose. All this talk about maintaining parameters, trace elements etc with water changes over the long term just does not hold up unless your tank has very little consumption. Not to mention doing water changes is an expensive and time consuming way to dose.

For example:

If you run your tank at 7.5 and use a salt that mixes to 9, and you do 20% water change per week. Even if your tank only uses 0.1 dkh per day, so you're at 6.8 after a week, with a 20% water change now you're only back up to about 7.25. So now the second week it's down to 6.5 and a 20% water change only brings it up to 7.

Now keep in mind this is with at least 2-3x the water change most people do and it only gets worse as corals grow and coralline starts to grow. Also keep in mind this happens with every element in the tank, trace elements and all.

A dosing solution with trace elements is the best way to go. It's more stable, easier and cheaper.

 

[scabbedwings616]

I’ve used a few different salts and reef Crystals pare by far my favorite. I keep my tank between 8.8 and 9.4 now. This is watched by a trident so it tests & day# a week. when I used tropical Marin, I couldn’t for the life of me keep acros. Dkh was 8.2 to 8.6 and was stable When I used Marin salt. I switched back 4 months ago to reef crystals and acrose are doing amazing. Stable and encRusting. It’s amazing to see again and happy again getting acros again.

 

[Thespammailaccount]

Ok here is where I’m at, I now get it’s easier to start low and dose if needed, I guess people dose the amount the corals use on a daily basis, not so easy to remove if you start with a level too high.
I am going for an LPS reef but if I go for the classic at 9, how do I keep the alk stable? If the corals don’t use much alk, wouldn’t water changes result in big swings? Hope that makes sense.

The alk in my salt mixes to 11.3-11.5 but generally 11.4 on the money. I dose alk with cal and mag daily to keep alk cal and mag at the same level 11.4. Four level scoops per five gallons. How much is my scoop? Not sure. But it mixes the salinity to match tank salinity. Top off is two small jugs a day. How much? Not sure. Alk cal mag and salinity say constant. This is what is important

 

[Reef.]

If you are going to keep stony corals, at some point you're going to need to dose. All this talk about maintaining parameters, trace elements etc with water changes over the long term just does not hold up unless your tank has very little consumption. Not to mention doing water changes is an expensive and time consuming way to dose.

For example:

If you run your tank at 7.5 and use a salt that mixes to 9, and you do 20% water change per week. Even if your tank only uses 0.1 dkh per day, so you're at 6.8 after a week, with a 20% water change now you're only back up to about 7.25. So now the second week it's down to 6.5 and a 20% water change only brings it up to 7.

Now keep in mind this is with at least 2-3x the water change most people do and it only gets worse as corals grow and coralline starts to grow. Also keep in mind this happens with every element in the tank, trace elements and all.

A dosing solution with trace elements is the best way to go. It's more stable, easier and cheaper.

I followed most of that, makes sense, the part that lost me was, how can you run a tank at 7.5 if your water is 9?

 

[Sisterlimonpot]

I followed most of that, makes sense, the part that lost me was, how can you run a tank at 7.5 if your water is 9?

I'm assuming he's making the point that if you add 10g of freshly mixed salt with a high dKH to 100g, the high dKH will be significantly diluted.

 

[Potatohead]

I followed most of that, makes sense, the part that lost me was, how can you run a tank at 7.5 if your water is 9?

On a new tank the alkalinity is going to closely match your newly mixed water, sure. In that scenario trying to keep up with demand with only water changes is even worse.

 

[ichthyoid]

I'm assuming he's making the point that if you add 10g of freshly mixed salt with a high dKH to 100g, the high dKH will be significantly diluted.

I think he’s making the point that it’s difficult, or impossible, to maintain stable levels using only water changes.

Even if levels in the new water are elevated, due to a combination of useage & dilution factors.

 

[Sisterlimonpot]

Now i'm just as confused as OP... hehe

 

[K7BMG]

Been looking into salt, I keep reading lower alkalinity is preferred in a salt, can someone please explain why this is the case? as I thought corals used alkalinity so the more the better?

This is a highly controversial subject in reefing.
People will go to great lengts to prove this one way or another with mathematical equations, and various stuff proving there theories and the like.

Its not that complex.
First off its your tank and it will NOT be like any other here.

EVERYONE DOSES, EVERYONE.
what is dosed? Alk, Ca, and Mag.
Many forms of dosing from Triton, to Ca reactors, two part, or individually.
In the end everyone doses.

Thoes that choose let me repeat here THAT CHOOSE a high DKH at 11 or so are all proponents of havingva salt mix with a high Alk.
This way they dont have to dose so much and the system can be more stable. Most of these folks are avid reefers with experience and older tanks mind you.

80% of the members here asking these questions are within a year or two of their first reef tank.
High Alk will have very negative results fast.
If there is one rule this hobby can teach is take it slow, and learn along the way.
So in the begining it is far more common to start at natures base line of 7ish and work your magic from that point.
So with that understanding is the real answer to your question.

 

[Pntbll687]

I keep my alk around 8.5-9.0, just because that's where instant ocean usually mixes to.

Just an anecdote, but have not had any success keeping lps in higher alk. Hammers, frogspawn, duncan all withered and receded when alk would be 10+. But I have found the opposite with sps, especially montipora, would grow like crazy with all at 11.

 

[SCReef'n]

As others have said. Pick a salt the matches the parameters your aiming for and dose to keep it there. If you wan 8dkh. Pick a salt that’s 8 dkh and dose allk to maintain that level as corals consume it. What you don’t want is to shoot for 8 dkh and use a salt mix that’s 12 dkh. Evrytime you do a WC. Your going to spike your alk and stress the tank.

 

[Reef.]

This is a highly controversial subject in reefing.
People will go to great lengts to prove this one way or another with mathematical equations, and various stuff proving there theories and the like.

Its not that complex.
First off its your tank and it will NOT be like any other here.

EVERYONE DOSES, EVERYONE.
what is dosed? Alk, Ca, and Mag.
Many forms of dosing from Triton, to Ca reactors, two part, or individually.
In the end everyone doses.

Thoes that choose let me repeat here THAT CHOOSE a high DKH at 11 or so are all proponents of havingva salt mix with a high Alk.
This way they dont have to dose so much and the system can be more stable. Most of these folks are avid reefers with experience and older tanks mind you.

80% of the members here asking these questions are within a year or two of their first reef tank.
High Alk will have very negative results fast.
If there is one rule this hobby can teach is take it slow, and learn along the way.
So in the begining it is far more common to start at natures base line of 7ish and work your magic from that point.
So with that understanding is the real answer to your question.

That settles it, I’m going for the TM pro at 7dkh, the classic is 9 so on the high side, I guess I can increase the dkh of the TM pro if needed later down the line.
Thanks for the stern tone I needed it!

 

[CollectOyster04]

A piece of advice for the newer reefers, regardless on where you decide to maintain your alk, etc., be sure to be testing...often. It's a pain to most, but this is how you will get to know your tank. Many of the tenured folks can tell you they wouldn't need to, they can tell just by looking at their corals. But in the beginning, testing, seeing the results and matching that to coral health (good or bad) will help you understand what's happening. Around month 5 of my tank(when I started adding the majority of my corals), my ritual was to test every evening(now I rely on my trident for the heavy lifting most of the time). This helped me see not only when I needed to start dosing, but also by how much (kind of touched upon previously). Especially in the beginning, a dosing pump will not be necessary. Hand dosing(using a spoon or other measuring device) will be just fine. Testing your freshly mixed salt helps too. Can't always trust what the manufacturer says everything will mix to. Helps to know exactly what you're putting in your tank. You can find info on how to raise or lower the freshly mixed water parameters with a quick search. As your tank matures, and your understanding on what's happening as the corals grow continues, testing becomes less critical (but still necessary at times). I'm a slow learner at most things, but once I did my due diligence (with testing), everything started to click. Sporadic testing imo does no good. It needs to be consistent to understand the relationships. It goes beyond the big 3(alk,ca,mg), but understanding those helps with everything else down the line. And you will find general consensus is for newer tanks to stay in the 7-9dkh range as opposed to 10+. Generally with higher alk levels, nutrients seems to become a bigger factor for overall coral health. Everything with reef tanks seems to play with cause and affects. Changing one thing can/will affect something else. This is why you hear many say go slow with changes. So you can monitor the change you made and to what affect it has.

 

[adobo]

Been looking into salt, I keep reading lower alkalinity is preferred in a salt, can someone please explain why this is the case? as I thought corals used alkalinity so the more the better?

I've been pondering this question also and was thinking of starting a thread when I ran across yours (good timing, eh?).

After reading the responses, I haven't seen one that resembles a convincing argument as to why "lower" alkalinity is preferred. In the first place, I think there should be a clear definition of what is meant by lower.

In my case, I am considering two salt options - Tropic Marin pro and Tropic Marin classic. What's the difference between the two? Let's look at the manufacturer's specs.

• Classic: approx. 9-10° KH, calcium approx. 380 ppm, magnesium approx. 1260 ppm
• Pro: approx. 7° KH, calcium approx. 440 ppm, magnesium approx. 1350 ppm

The conventional wisdom seems to be that the pro variety is preferred for reef tanks. That's what the BRS guys push and seems to be what many of the Tropic Marin users are using (based on a poll I saw here on R2R recently). Looking at the manufacturer's specs, we can see that the pro variety has more calcium and magnesium yet is lower in alkalinity.

If memory serves, it is difficult to produce a salt that is high in alkalinity as well as calcium and magnesium. Its like a seasaw between alkalinity and calcium as to the maximum amount you can keep in solution. If you try to elevate either or both too much, you get precipitation. Maybe someone who knows a lick about chemistry can keep me honest on this and perhaps elaborate.

If you keep stony corals, you are always concerned about calcium and mindful about magnesium. For these reasons, a salt that has "elevated" calcium and magnesium would seem superior. With that said, you still need to keep an eye out for alkalinity.

This is the "theory" as I understand it. Now, let's talk about "in real life". BRS ran some tests on salts. The numbers they showed is that Tropic Marin pro mixed with around 420ppm calcium and 7dkh. Tropic Marin classic mixed with around 410ppm calcium and 8-9 dkh. I'm working off of memory so I might be off a tad. Based on the real life numbers that BRS shared, I have no flipping idea why Tropic Marin pro is supposedly better. Is it because of 10ppm difference in calcium? I posed this same question to someone at BRS. The answer was every bit as unconvincing as the ones you have gotten on your thread.

So back to where I started - I have the exact same question as you - why is a salt with lower dkh supposedly better than one that has higher dkh? To phrase the question more precisely, let me add, "assuming all else is relatively equal."

The others posting on this thread about how you need to use salt that is close to what your target parameters are ... they are right but they are answering an entirely different question altogether.

One last bit - all this "keep your alkalinity low" business seems strange to me. Tropic Marin pro is a "johnny come lately" salt. Hobbyists have been using Tropic Marin classic with its "elevated" alkalinity for decades to keep the most beautiful reef tanks.

 

[Seaspirit]

As a new reefer (just have my first quarantine tank set up), I appreciate everyone's input on this thread. My 10 g tank has been running a month, has some zoas, a finger leather, xenia and some green star polyps, clownfish, some ricordeas and CUC. Weekly 10% water changes. All seem to be doing great except the zoas aren't very happy. Most of what I've read says to target alkalinity to 9 (and recently I ordered corraline algae and their instructions say to keep alkalinity at 8). My IO crystals mix to dKh of 11 and when I test I'm getting around 10.5, which is certainly higher than what I want in this simple little tank. At the same time, my pH has been low (7.8 or even lower), which made NO sense to me with high alkalinity, unless I'm just not aerating the tank enough and it's carbon dioxide building up. So I'm doing more aeration to try to raise pH and have no idea how to lower my dKh (still learning), plus the tank is SO new that I don't yet know what it's "normal" levels will be. I'd love to be able to use a salt mix which starts me at 9 dKH and then be able to supplement calcium and alkalinity and/or magnesium as needed. For me this QT is like a rehearsal for my 90 gallon which is on order.

I watched the BRS instructional video on calcium, carbonate and magnesium and it was excellent. I get that calcium and carbonate like to bind together but when they do they become unavailable to corals, so we'd rather have them floating around loose in the water column. Magnesium is what keeps them from hooking together. My little tank's magnesium is a little low and what worries me is that if I add a little, it will make more carbonate be free (unbound) which will raise my alkalinity, and I want to LOWER it. But on the other hand I don't like having low magnesium. It's so true that everything relates to everything else!

And yes, I know my tank is so new I probably should just leave it alone and see what it settles out to be. It just bugs me that every time I do a water change I'm adding in my high alkalinity IO salt mix and I lose hope of getting to 8 or 9 dKh. Didn't know where to look for other options. This discussion is really informative, thanks from a newbie!