Do low ALK affect sps growth?

[Saltwater gardens]

For the past year I've always had a low alkalinity between the range of 7.8 and 6.4, but never worried since my tank was with soft corals only. But two months ago I bought my first SPS corals and I havent been able to raise my alkalinity above 8.7, and keeps dropping to 7.2 - 7.8. So I havent noticed any good growth. I dose Reef builder by Seachem 25 grams per week (12.5 on tuesdays and 12.5 on fridays).

Tank parameters (chcked saturday 18)
Ca - 420
Mg- 1400
Alk - 8.1
pH - 8.0
Salinity - 1.026
Temperature range 80 - 78 F
Tank size - 80 gallon
Lighting - RadionXR30w pro (they recieved between 175 - 200 PAR, 10 hours a day)
Water movement - Flow eductor 1"

Three times a week I add 4ml of Reef Energy A and B

 

[Randy Holmes-Farley Verified Community Expert]

Hard corals can grow fine at an alkalintkiy of 7-8 dKH, but some may grow faster at higher alkalinity.

Unless high growth is a goal, I wouldn't worry about it.

Also, if your tank is a ULNS tank (ultra low nutrient) then it may be true that alk in the 7-8 dKH range may be better to avoid "burnt tips" that might come with higher alkalinity.

 

[Saltwater gardens]

High growth is a goal I want to achieve. So I'am running two types of filtration; Reef Octopus skimmer BH - 90 and 30 lbs of live rock with 5 mangrooves. Rizhophora mangle, if the specie do matter. Plus some Thalassia testudinum.

Alkalinity between 7-8 dKH could burnt the tips of my acros and birdnest? Should it be higher in the range of 9-11 dKH?

Thanks Randy for the reply.

 

[Randy Holmes-Farley Verified Community Expert]

I don't know if you have low nutrients, but if you do, then higher alk might result in burnt tips.

I'd raise it very slowly and stop if that seems to happen.

Higher pH will also potentially help growth.

 

[Saltwater gardens]

What are the best ways to increase my pH? Is there any article I could read?

Thanks

 

[Randy Holmes-Farley Verified Community Expert]

Sure:

Low pH: Causes and Cures by Randy Holmes-Farley - Reefkeeping.com

The best ways include limewater, fresh air, an airline to a skimmer inlet, growing macroalgae, and a CO2 scrubber on a skimmer inlet.