Why is lower alkalinity preferred?

[Potatohead]

Why do people feel 7 is the low end of acceptable? There are absolutely very successful tanks running in the low 6's and even some in the 5's. Personally I would probably try to run my tank lower than 7 but I don't want to drop my pH any more.

A lot of salts exist mixing up in the 11+ range because, IMO, it was common thought 20 years ago that you could just maintain alk with water changes. I have explained earlier in the thread why that line of thinking doesn't make much sense today. I believe those brands still continue to make salts with that kind of alk level because a lot of old school people still run their tanks that way, and teach new people that way, which is fine.

The other part of this is the increased growth from higher alk. Again I am not sold on this personally, but if it is in fact the case I'd probably only do it in a frag tank or something. Faster growth in a display can absolutely be a bad thing and even running at 7 things grow fast enough to see daily changes.

 

[Seaspirit]

I am no expert on aquarium salts but my impression is that TM pro is about as good a choice as you can make. Many of the others are not bad choices either but TM pro seems to check many of the boxes.

Having said that, if your objective is to drive you pH higher (to more "normal" levels), I think just switching to TM pro would be insufficient. At some point, the CO2 in the ambient air will continue to have impact on the pH of your aquarium. I would even not be surprised if you continue to see the current levels you are seeing today.

I have the same problem as you - my pH gravitates toward 7.8. I open the window in that room (and suck some air in by turning on some fans) and the pH increases. So that seems to work and is ok for now but its entirely too manual. I am moving towards a CO2 scrubber so that I can increase pH without having to open windows every day.

Anyway, good luck with it.

Quick update. I stuck an air stone in the "sump" back of my AIO nano tank and my pH jumped from 7.8 to 8.05. HOORAY! Yes I still open up the balcony door as frequently as possible. Also have a theory that with my new TM Pro salt (alkalinity of 7), if I dose additional alk to get up to the 8 to 9 range it might push my pH up a little bit too. Think that's what it says on the bottle of something I bought the other day. I think a CO2 scrubber would be too much for my little "quarantine" tank but I'll look into it. Good luck to you too!

 

[adobo]

Quick update. I stuck an air stone in the "sump" back of my AIO nano tank and my pH jumped from 7.8 to 8.05. HOORAY! Yes I still open up the balcony door as frequently as possible. Also have a theory that with my new TM Pro salt (alkalinity of 7), if I dose additional alk to get up to the 8 to 9 range it might push my pH up a little bit too. Think that's what it says on the bottle of something I bought the other day. I think a CO2 scrubber would be too much for my little "quarantine" tank but I'll look into it. Good luck to you too!

Sorry, I wasn't recommending a CO2 scrubber for your tank. Simply saying that I doubt that just switching salt in of itself would be sufficient to bump your pH up. I guess what I was implying is that you need to get fresh air in that room regularly.

As for me, opening a window regularly in the room where my reef tank is located is a hassle (for several reasons that I won't bother to go into.) So, I bought an off the shelf "CO2 scrubber solution". I hooked it up about 4 hours ago. pH is up to 8.21 from 7.99. I'm not really sure what the upper limits of the pH will be if I leave the scrubber online 24x7 so I will need to think of a way to keep the pH at a consistent level. But suffice it to say, a CO2 scrubber works - or at least, it seems to work on my tank.

 

[Jon Warner]

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.

Here's how I've been explaining it for 25+ years...

Saltwater Chemistry is like a bucket. You can fill the bucket with Water and Sodium, Calcium and Magnesium... Carbonates and Sulfates...

But if you add too much of something, it makes the bucket overflow (seen in the aquarium as elements "falling out of solution")

So... can you add extra Calcium and Magnesium to otherwise NSW and be OK? Sure... But increase dKH to 15 and Calcium to 550 mg/l and Magnesium to 1600 mg/l and you've got a "snowstorm". AKA... the bucket "overflowed".

 

[ReefPig]

Why do people feel 7 is the low end of acceptable? There are absolutely very successful tanks running in the low 6's and even some in the 5's. Personally I would probably try to run my tank lower than 7 but I don't want to drop my pH any more.

A lot of salts exist mixing up in the 11+ range because, IMO, it was common thought 20 years ago that you could just maintain alk with water changes. I have explained earlier in the thread why that line of thinking doesn't make much sense today. I believe those brands still continue to make salts with that kind of alk level because a lot of old school people still run their tanks that way, and teach new people that way, which is fine.

The other part of this is the increased growth from higher alk. Again I am not sold on this personally, but if it is in fact the case I'd probably only do it in a frag tank or something. Faster growth in a display can absolutely be a bad thing and even running at 7 things grow fast enough to see daily changes.

My question would be, can you point me to a “successful“ SPS tank currently running at 5 or 6 please?

My definition of successful is, bright colours and strong growth, over an extended period of time.

I’ve also seen some tanks running at this, but they are either softie / LPS, this is fine for them, but not SPS imo.

 

[Seaspirit]

Sorry, I wasn't recommending a CO2 scrubber for your tank. Simply saying that I doubt that just switching salt in of itself would be sufficient to bump your pH up. I guess what I was implying is that you need to get fresh air in that room regularly.

As for me, opening a window regularly in the room where my reef tank is located is a hassle (for several reasons that I won't bother to go into.) So, I bought an off the shelf "CO2 scrubber solution". I hooked it up about 4 hours ago. pH is up to 8.21 from 7.99. I'm not really sure what the upper limits of the pH will be if I leave the scrubber online 24x7 so I will need to think of a way to keep the pH at a consistent level. But suffice it to say, a CO2 scrubber works - or at least, it seems to work on my tank.

What CO2 scrubber solution did you get? My pH has settled back into the 7.8 range even with the air stone (sigh). I'm setting up a little HOB refugium hoping the extra photosynthesis will help.

 

[adobo]

What CO2 scrubber solution did you get? My pH has settled back into the 7.8 range even with the air stone (sigh). I'm setting up a little HOB refugium hoping the extra photosynthesis will help.

I bought an ice cap co2 scrubber but to be honest, there is nothing fancy about it. I could have done the same thing for about 2/3 the price using a water filter canister.

My tank is running about 8.15 to 8.25 pH depending on how I have it set up. I use a tee and a ball valve to get some room air in the mix. If I just use CO2 scrubbed air into my skimmer, pH continues to climb to 8.3. Not sure how high it would go but at about 8.25, I open the valve a bit and let pH drop to 8.15 before I close the valve a little again and let the skimmer suck mostly CO2 scrubbed air.

 

[ReefPig]

As a build on my earlier comments...

This morning I've just had 100L of NSW delivered, this is the first time I've done a water change with NSW, but I did originally set my tank up with it a year ago, albeit at the time I didn't test it.

I've just tested salinity and dKH, with the results of:

Hanna Alk: 8.1dKH
Salifert Alk: 7.8-7.9dKH
Hanna Salinity: 34.7
Refractometer: ~34.5

This is using the biggest NSW supplier in the UK and they ship a LOT of water around.
It's collected about 2 miles off shore to the north of the UK.

Who said NSW isn't 8dKH?

 

[Seaspirit]

I bought an ice cap co2 scrubber but to be honest, there is nothing fancy about it. I could have done the same thing for about 2/3 the price using a water filter canister.

My tank is running about 8.15 to 8.25 pH depending on how I have it set up. I use a tee and a ball valve to get some room air in the mix. If I just use CO2 scrubbed air into my skimmer, pH continues to climb to 8.3. Not sure how high it would go but at about 8.25, I open the valve a bit and let pH drop to 8.15 before I close the valve a little again and let the skimmer suck mostly CO2 scrubbed air.

Sounds like you have it tuned in nicely, good job! My chaeto arrives in a week and I hope that stuff gets to work on my CO2. Am hoping my 90 gal tank (in big living room with better air flow) won’t have pH issues when it gets installed, but if it does I’ve sure learned some things that might help. Thanks!

 

[Potatohead]

My question would be, can you point me to a “successful“ SPS tank currently running at 5 or 6 please?

My definition of successful is, bright colours and strong growth, over an extended period of time.

I’ve also seen some tanks running at this, but they are either softie / LPS, this is fine for them, but not SPS imo.

 

[Potatohead]

As a build on my earlier comments...

This morning I've just had 100L of NSW delivered, this is the first time I've done a water change with NSW, but I did originally set my tank up with it a year ago, albeit at the time I didn't test it.

I've just tested salinity and dKH, with the results of:

Hanna Alk: 8.1dKH
Salifert Alk: 7.8-7.9dKH
Hanna Salinity: 34.7
Refractometer: ~34.5

This is using the biggest NSW supplier in the UK and they ship a LOT of water around.
It's collected about 2 miles off shore to the north of the UK.

Who said NSW isn't 8dKH?

Thanks average dkh of nsw in areas where corals actually grow is about 7