Keeping Alk High?? Benefits?

[Sangheili]

Alk in the 8-9 range is what all of my systems like. When it rises above 9 I see stress on the acros. My tanks are not ULNS, but they also do not show Nitrate when testing.

My advice:
If you have consistently 1-5 ppm Nitrate when you test, you can run an SPS system at 10-12 alk.
If you always test nitrate below 1ppm or even zero, stay in the 8-9 range.

This is greatly oversimplifying things, but it should be appropriate for most tanks. As Randy said, higher alk will force the coral to grow faster and without proper nutrients it will force the coral to use more energy then it can provide itself.

 

[Hans-Werner]

In my experience best KH is more connected to phosphate. You see it when you use phosphate adsorber. With less than 0,1 ppm reactive phosphate (what shows up with a test kit) you should keep KH at 6 to 9. Natural KH is just 6.5 at 35 psu salinity so it would be strange if corals would really need higher KH under close-to-natural conditions.

 

[Jongalt26]

Sangheili,
I think phosphates must be present as well, i ran alk per RSCP spec (12.1). I was running kalkwasser (which i read can pull out some phosphates) and when i added GFO to my system i ended up with shrinkage and burnt tips.

 

[DamianOZ]

Fastest growth SPS for me = undetectable nutrients with 6.5dKH to 6.8dKH alkalinity
undetectable nutrients + elevated alkalinity = RTN
Elevated nutrients = slow growth,

Not sure where the elevated alkalinity = faster growth come from, I experience the opposite. Maybe with elevated nutrients, more C helps reduce slower growth.
Higher alkalinity is more dangerous than low, raising Alk to give more room for error is a false theory IMO., at least with NSW nutrient levels

 

[Jongalt26]

I think a high Alk and elevated nutrients can produce fast growth.

 

[Randy Holmes-Farley Verified Community Expert]

Not sure where the elevated alkalinity = faster growth come from, I experience the opposite.

It's published in the scientific literature, and many folks find it to be true.

 

[DamianOZ]

It's published in the scientific literature, and many folks find it to be true.

Sure, I repeated the same theory back in the 1990/00s too. But, what I am unsure about is what fast growth claims are comparing to.
Is it a (nutrient rich + >9dKH) vs (nutrient rich + <7.5dKH)
or (nutrient rich + >9dKH) vs (ULN + <7dKH)
IME (ULN + <7dKH) = fastest growth, other conditions equal and not just some, all. Although some SPS seem to grow well in (nutrient rich + >9dKH), many do not.

Most SPS grow very rapidly in NSW conditions, assuming lighting and feeding requirements are not limiting.
In many aquariums systems, SPS slow down or even die. This would indicate that our changes are retarding growth. It appears that we can counteract some slowing in same SPS by altering certain conditions, like increasing KH in nutrient rich systems.
IMO, altering KH sees insignificant changes compared to other aspects. Maintaining ionic balance, influencing coral to regulate zoanthellae, lighting, feeding, temperature, etc have greater impact on growth.

What I do believe though is, advising people to run high KH is dangerous. It only works in nutrient rich systems, in ULN, high alk will cause some SPS to TN, where as low KH levels will cause no noticeable problems, I've run Alk as low as 5dKH with out any noticeable ill effects. But when KH gets too high and you notice ill effects, its too late, TN is not reversible.

 

[Hans-Werner]

I never had success with high alkalinity, I agree with Damian, and I always had low nutrients. For me 7° was the limit, even 8° resulted in stressed corals and worse growth. If I remember it right the scientific experiments regarding alkalinity were short term experiments running over days and not months and years which a reef tank should. Enhanced calcification on a short term may not be a good indicator for coral health and growth on the medium and long term.