Why do a lot of reefers keep a lower alk in their tank (8-9)?

[Fishurama]

I run GFO and carbon making it hard to even keep it at 8. I usually test at 7.5-7.8 and try to keep it up around 8 to 8.5

 

[Barnabie Mejia]

I run GFO and carbon making it hard to even keep it at 8. I usually test at 7.5-7.8 and try to keep it up around 8 to 8.5

How does the GFO and carbon make it hard to keep it at 8? I pulled my gfo and carbon off line a while back and my alk is at 10.5 and if I remember correctly it was at 9.5 when it was on.... not saying you’re wrong I just think you’re on to something that might make sense in my tank!

Thanks

Barnabie

 

[Phyber]

Question for the more experienced reefers:

I dose and am keeping my levels where my IO RC salt got my tank to after religious water changes:
Alk: 9.9
Cal: 490
Mag: 1425
Sg: 1.026

However, my nutrients for Nitrate and Phosphate continuously come back as undetectable on my Salifert tests.

Ive tried feeding more and no water changes (was doing a 20g change once every other week on a 65g tank) but am seeing no nutrient readings.

Am I good or bad for a mixed reef?

 

[CMO]

Others correct me if I’m wrong but this is how I understand it- ALK should have a direct correlation between Mag and Cal numbers. If Mag and Cal is high the ALK should be kept higher and vice versa. The biggest thing, whether you keep your ALK high or low, as with anything in a reef tank, is to keep it consistent and properly acclimate any livestock going into your tank. Everyone seems to have success in this hobby at all different water level parameters, within in reason of course. Just keep it consistent.

Not sure about this scientifically but I can at least say that in my experience this does not seem to matter. I run low alk at 7.5 with somewhat high cal and mag at ~460 and ~1400, respectively, and get very good results with all corals, though my system is SPS dominant.

 

[FishDoc]

The Trident.

Why? I due suspect you’re correct due to the procedural nature of the two tests and the generally assumed increased accuracy of titration vs colorimetric but do you have evidence this is in fact true?

 

[Earl Karl]

Question for the more experienced reefers:

I dose and am keeping my levels where my IO RC salt got my tank to after religious water changes:
Alk: 9.9
Cal: 490
Mag: 1425
Sg: 1.026

However, my nutrients for Nitrate and Phosphate continuously come back as undetectable on my Salifert tests.

Ive tried feeding more and no water changes (was doing a 20g change once every other week on a 65g tank) but am seeing no nutrient readings.

Am I good or bad for a mixed reef?

No nutrients and high alk. can cause problems for especially sps. The skeleton will outpace the tissue and you will get something called burnt tips, which is essentially exposed skeleton.

Also titration test kits WILL lie to you, but lets just say that's not a factor. Just be patient for nutrients to rise up. You can add NO3 and PO4 to the tank, but that could potentially add more complications to your reef. I would just keep feeding and be patient.

I have 0.01 ppm PO4 and >1 ppm NO3 with 9.5 dkH. That is VERY low for my reef's alk. but I have a giant refugium that sucks up all the nutrients. However, I combat this with broadcasting reef roids (any form of zooplankton will work) every night. That is somewhat how the ocean works as well. Despite very low nutrients in NSW (essentially same as my reef's parameters), corals consume zooplankton during night to compensate for nutrients. However, NSW's alk. is at 7, so low nutrients is not a big deal in the ocean.

 

[Fishurama]

How does the GFO and carbon make it hard to keep it at 8? I pulled my gfo and carbon off line a while back and my alk is at 10.5 and if I remember correctly it was at 9.5 when it was on.... not saying you’re wrong I just think you’re on to something that might make sense in my tank!

Thanks

Barnabie

To put it simply the GFO and Carbon(mainly GFO) tend to soak some up while doing its main job(phosphate) thus allowing your corals more free alk not trapped by phosphates, leaving you with less alk overall since the corals are also able to use more of it do to less phosphates.

the more scientific explanation.
"Many aquarists using GFO have reported unusually extensive precipitation of carbonates on the solid GFO, and elsewhere in the system. Such precipitation can, for example, be a contributing factor in the caking of such materials, and can coat other surfaces in the aquarium. This precipitation can also contribute to a drop in alkalinity and possibly pH as it removes carbonate from the water column. The effect of calcium will be similar, but smaller on a percentage basis, with a drop of only 20 ppm calcium for every 1 meq/L (2.8 dkH) drop in alkalinity. Increased calcification by corals and coralline algae (possibly spurred by reduced phosphate) can also cause similar drops in calcium, alkalinity, and pH. "

http://www.reefkeeping.com/issues/2004-11/rhf/index.php

 

[GregDaKeg]

When running Zeovit I ran mine at 6.8-7.0

Otherwise, generally recommend 8-9, NSW is usually ~7 but I like that extra degree or so of buffer room.

Nothing wrong with keeping 9-11 IMO just have to make sure nutrient levels dont get low.
What is NSW?

 

[Earl Karl]

NSW=Natural Seawater

 

[GregDaKeg]

NSW=Natural Seawater

Thanks. Still new.

 

[Blitheran]

I just chose a number.... everywhere said 7-11 is a key alkalinity number so I picked 9. Happy middle, brs also did an investigate about higher levels provided better growth so I will stick to the 9dkh and just maintain it as best as I can do. No science behind my method just decided on a number and stuck to it. All my sps are encrusting or growing

 

[vetteguy53081]

I run mine a little higher (9-9.5) due to having a mixed reef

 

[Gino Rodriguez]

Others correct me if I’m wrong but this is how I understand it- ALK should have a direct correlation between Mag and Cal numbers. If Mag and Cal is high the ALK should be kept higher and vice versa. The biggest thing, whether you keep your ALK high or low, as with anything in a reef tank, is to keep it consistent and properly acclimate any livestock going into your tank. Everyone seems to have success in this hobby at all different water level parameters, within in reason of course. Just keep it consistent.

I too subscribe to a lot of the “ratios” hypothesis on cal/alk and nitrate/phosphate

 

[Gino Rodriguez]

As I explained earlier, nutrients must be in balance with alkalinity to keep up with the pace of skeleton and tissue growth.

Lower alk. is only better for low nutrient tanks. Nutrients correlate to tissue growth while alkalinity correlates to skeleton growth. In low nutrient tanks, high alkalinity will cause the skeleton to grow faster than the tissue, resulting in burnt tips in mainly acros. With low alk., you won't get the growth, but you will have amazing colors. This is more catered to fully matured reef packed with colonies.

In higher nutrient tanks, lower alkalinity would create disgusting color (subjective to point of view however) with poor growth. With higher alkalinity along with higher nutrients, both can keep up with each other's pace resulting in much faster tissue and skeleton growth, however, due to higher nutrients, you won't get those amazing colors. More catered to frags that you just want to grow out fast as possible.

I have mine at the happy medium however, I still get fast growth and amazing colors.

Super insightful! I’m going to see if I can replicate

 

[Earl Karl]

Super insightful! I’m going to see if I can replicate

What I used to do was first start with 12 dkH, 0.12 ppm PO4, and 2 ppm NO3. I would get insane acro growth but colors would be meh. Then after I get the growth I want, I would very slowly lower my parameters to 7 dkH, 0.03 ppm PO4, and >1 ppm NO3. After settling to the new parameters, which takes a while, my acros would then get amazing coloration.

One day, I was testing two of the same acro frags. I put one in the tank where I used the method I mentioned above to grow out my acros, and one in another tank that was consistently 9-9.5 dkH. I would find out that even though growth at 9-9.5 dkH was slower than if I kept it at 12 dkH, by the time the acros colored up at 7 dkH, the acros in 9-9.5 dkH has actually grew a bit more and still has nice coloration without changing any parameter. So I just stuck with 9-9.5 for the sake of stability.

 

[Gino Rodriguez]

What I used to do was first start with 12 dkH, 0.12 ppm PO4, and 2 ppm NO3. I would get insane acro growth but colors would be meh. Then after I get the growth I want, I would very slowly lower my parameters to 7 dkH, 0.03 ppm PO4, and >1 ppm NO3. After settling to the new parameters, which takes a while, my acros would then get amazing coloration.

One day, I was testing two of the same acro frag. I put one in the tank where I used the method I mentioned above to grow out my acros, and one in another tank that was consistently 9-9.5 dkH. I would find out that even though growth at 9-9.5 dkH was slower than if I kept it at 12 dkH, by the time the acros colored up at 7 dkH, the acros in 9-9.5 dkH has actually grew a bit more and still has nice coloration without changing any parameter. So I just stuck with 9-9.5 for the sake of stability.

Great stuff,Gotta love geeking out on technical reefing

 

[JimWelsh]

Why? I due suspect you’re correct due to the procedural nature of the two tests and the generally assumed increased accuracy of titration vs colorimetric but do you have evidence this is in fact true?

I wouldn't have invented the Trident if I didn't.

 

[Da8]

7,5 but want to get to 8,2

 

[Magellan]

I have 0.01 ppm PO4 and >1 ppm NO3 with 9.5 dkH. That is VERY low for my reef's alk. but I have a giant refugium that sucks up all the nutrients. However, I combat this with broadcasting reef roids (any form of zooplankton will work) every night. That is somewhat how the ocean works as well. Despite very low nutrients in NSW (essentially same as my reef's parameters), corals consume zooplankton during night to compensate for nutrients. However, NSW's alk. is at 7, so low nutrients is not a big deal in the ocean.

I keep my alk at about 8.3, and have very similar nutrient levels. I feed my corals 2-3x a day (depending on whether or not I broadcast reef roids). How important do you think feeding at night is, and would it matter if my corals are already used to feeding during the day?

 

[Earl Karl]

I keep my alk at about 8.3, and have very similar nutrient levels. I feed my corals 2-3x a day (depending on whether or not I broadcast reef roids). How important do you think feeding at night is, and would it matter if my corals are already used to feeding during the day?

Corals get majority of their food from photosynthesis, in the form of Carbon. However, they still need to consume Nitrogen and Phosphorus as like Carbon, they are the building blocks of life (this applies to ALL organisms). One way of getting N and P is from zooplankton (that is pretty much what reef roids is).

However, corals don't consume enormous amounts of zooplankton as we think they do. It's the reason why they look bleached (but shiny colored) when a wholesaler brings them in from a transshipment. Just low alk. of 7 dkH, very low nutrients, getting cooked by the sun in the wild. After a while under artificial lights and water, they get more richer colors due to higher nutrients and less light compare to the sun.

The main reason corals are used to consuming zooplankton during the night is because that is when zooplankton arises into the water column. I don't think it would make a difference whether you feed during the day or night. You can always teach coral when it is feeding time. However, since corals mainly feed throughout the night in nature and I'm usually out of home during the day, I just broadcast reef roids during night. However, there is nothing wrong with feeding during the day.