Is Alk stability Key to SPS Health

[cumbeje]

I have a 730 gallon mixed SPS tank. Over 6 years I have had ups and downs. The most frustrating has been episodes of certain SPS coral dying from the base up. It seems in this episodes its a time when ALK fell below 8. Anyone else seen this? Also, unfortunately it doesn't seem to stop once it starts in most cases.

 

[Ike]

I think alkalinity fluctuation is not as damaging as most make it out to be, as long as it's within a certain range. However, stability is certainly something to strive for. Also, alkalinity dropping below 8 has never been an issue for me, especially since I usually maintain it in the 6.5-7.5 range.

 

[ihavecrabs]

I have a 730 gallon mixed SPS tank. Over 6 years I have had ups and downs. The most frustrating has been episodes of certain SPS coral dying from the base up. It seems in this episodes its a time when ALK fell below 8. Anyone else seen this? Also, unfortunately it doesn't seem to stop once it starts in most cases.

Mine tended to have issues above 9.5 and below 8. When I keep mine steady at 9 I tend to get the best growth and colors.

And yes, I do believe alkalinity is one of the most important parameters to keep stable once you have the basics down (temp, salinity, no3, etc)

 

[drawman]

+1 on stability with alkalinity. What do you normally keep it alkalinity at? If it's dropping from let's say 10 or higher that could be a big jump.

 

[cumbeje]

Mine is usually around 8.4. Just a little change below 8 seems to set off losing some SPS.

 

[FranklinDattein]

Alk swing is arguably the most common reason for SPS issues, in thriving tanks. It seems volume plays a role in how much alk variation is fine and avoiding swings greater than .5dkh/day is a common practice and works well even on small volumes of water.
It being in the low side is not so much of s problem, many of us keep it at 7dkh. The swing is the problem.

 

[ihavecrabs]

Alk swing is arguably the most common reason for SPS issues, in thriving tanks. It seems volume plays a role in how much alk variation is fine and avoiding swings greater than .5dkh/day is a common practice and works well even on small volumes of water.
It being in the low side is not so much of s problem, many of us keep it at 7dkh. The swing is the problem.

Agreed. Once I started dosing every hour and got everything dialed in, my SPS have taken off and never looked happier.

 

[Randy Holmes-Farley Verified Community Expert]

I have a 730 gallon mixed SPS tank. Over 6 years I have had ups and downs. The most frustrating has been episodes of certain SPS coral dying from the base up. It seems in this episodes its a time when ALK fell below 8. Anyone else seen this? Also, unfortunately it doesn't seem to stop once it starts in most cases.

Alk below 8 dKH is fine, but big swings may not be optimal. That said, your swing doesn't look very big and I would guess the answer is elsewhere.

 

[Fourstars]

Does anybody know of any studies on alkalinty/ calcium swings done on an actual reef? I know it's a large volume of water, but you would think that the localized uptake would cause a daily swing.

 

[drawman]

Does anybody know of any studies on alkalinty/ calcium swings done on an actual reef? I know it's a large volume of water, but you would think that the localized uptake would cause a daily swing.

Don't know of any studies but my assumption would be the massive amounts of replenishing saltwater would make any uptake negligible.

 

[Randy Holmes-Farley Verified Community Expert]

I don't think there are any substantial daily alk swings on an open reef. pH, yes, but not alk. Closed lagoons might, but in general, alk is not being created on a reef, just washed in by currents.

 

[Myka]

I agree with Randy, a swing from 8.4 dKH to 8.0 dKH is probably not going to be an issue. A swing from 8.4 to 7.0 dKH may be enough to cause issue. IME, an up swing is more likely to cause the issues you are describing.

That said, for optimal Acropora health, the alkalinity level should be a reflection of the NO3 and PO4 concentrations. If NO3 and PO4 are very low or undetectable, you can get alkalinity burn in the tips of the Acros if alkalinity gets above about 8-8.5 dKH (tanks vary, and NO3 and PO4 testing can be misleading). If NO3 and PO4 are medium or high, then the SPS can handle higher alkalinity without issue. The trend nowadays with Acros is to keep the "big three" parameters as close to natural seawater as possible, and to keep NO3 and PO4 slightly elevated from natural seawater levels (a little is good, none is "bad"), rather than keeping NO3 and PO4 at "0 ppm" as used to be considered optimal. Thus, the trend is to keep calcium around 410 ppm, alkalinity around 7.1 dKH, magnesium around 1240 ppm, NO3 around 0.5-2 ppm, and PO4 around 0.01-0.06 ppm. Acros tend to be hardier if you keep them in these ranges.

Now, LET'S SEE SOME PICS OF THIS TANK!!!

 

[Hans-Werner]

Yes, in my opinion alk is the most important single parameter for SPS. The optimum alk depends from the phosphate concentrations. With low phosphate concentrations (ULNS) you soon get problems with high alkalinity. I regularly had problems when alk was above 8.0. I knew a guy who regularly had problems when trying to remove phosphates and rise alk to 9. I think problems with low alk are quite rare. In fact alk of natural seawater is quite exactly 6.5 (ca. 2300 to 2340 µmol/kg normalized total alkalinity according to Millero) at 35 psu salinity and there is only little variation in the oceans. So SPS should be used to and grow at this "low" alkalinity.

 

[Tapio]

I only get alarmed if alk is below 6. I like it to be 7-9. Not higher. Worked for years.

 

[jd371]

I only get alarmed if alk is below 6. I like it to be 7-9. Not higher. Worked for years.

This. I try and keep it at 8.5. I do get swings now and then down to 7.8 and up to 9.2.

 

[revhtree Verified Admin]

Interesting topic! Would love more input!

 

[cginter]

Do you guys dose every hour 24hrs or just during the lights off period?

 

[rock_lobster]

Below 7 is the danger zone for me. I had it drop to 6.4 once and all the softies nearly died at the same time. SPS all died. So I aim to always keep above 7 and below 8. Daily swing greater than .5 becomes risky I can see some of the softies close up SPS not as badly affected. 1 dkh swing in 24 hrs and Ive definitely seen problems. I think it depends on if you have a mixed reef though. Softies go first.

 

[sil40sx]

Alk below 8 dKH is fine, but big swings may not be optimal. That said, your swing doesn't look very big and I would guess the answer is elsewhere.

Mine is 7.44 in the morning, and 7.50 late at night. And having difficulty keeping SPS alive. Calcium is stable around 450ish. Rest of the parameters are on recommended range as well.

People recommended to increase my Alk in my thread. But I'm still unsure what to do because I get mixed suggestions. And I'm afraid I will mess up my calcium stability.

Sorry OP for butting in.

 

[erk]

I find that alk stability is important, but that Mg is the key to that stability. If I see a swing of +/- 100ppm or greater of Mg, the coral begin to deteriorate due to the subsequent swing in alk. This is what I have observed over the last couple years of coral keeping. I maintain Mg at ~1400ppm as this is what works for my tank. This keeps alk at ~9dkh and Ca at ~430ppm with standard two part dosing.