CO2 - macro algae - kalk - vinegar

[jimsflies]

I have finally been able to grow some macro (caulerpa). However, it seems to do very well for awhile and then die back. I haven't been able to figure out why it is doing this.

Recently, I started thinking that it could be related to when I change out my Kalk dispenser (connected to the osmolator). The fresh Kalk tends to cause a few day spike in the pH (8.4). It actually would be higher right after replenishing the lime in the kalk dispenser, but I have the top off on controlled via pH to prevent higher spikes. Typically, my pH is in the 8.2's.

Here is a link to my graph showing my pH. (http://reef.jimsflies.com/graphs.php?params=pH&startDate=2007-02-15&endDate=2007-02-25)Kalk was replaced on 2/19. You can see that the peaks were above 8.4 after this date with night pH's around 8.2. Versus day peaks at 8.3 and night pH's around 8.1. ...I know this sounds like splitting hairs, and the graph is some what tedious to see what I am talking about.

On further thinking, I am wondering if it's not so much the pH causing the issue as much a deficiency in CO2 because of the reaction of lime occuring in the tank. (The macro is being limited by CO2.)

Is there any info out there related to this or has anyone had similar issues and figured out the solution? Is it possible that CO2 or pH could be causing the issues with the macro algae?

I currently use an osmolator and kalk dispenser for kalkwasser. I'm not sure if I can even add vinegar to the kalk using this setup? But do you think it would help, by providing enough CO2 to not have as many effects on the reef system? Any info on vinegar + kalk would also be appreciated.

[Randy Holmes-Farley]

I've actually find macroalgae to not do well adding vinegar, and I believe that is because bacteria thriving on the vinegar compete with the macroalgae for nutrients.

Adding vinegar to a limewater reactor is technically difficult, and few if any people do it.

Ever add iron? That seems to help Caulerpa racemosa considerably.

Many macroalgae grow fine at elevated pH, because they use bicarbonate as a source of CO2, but some do not. I do not have data for Caulerpa, however:

Photosynthesis and the Reef Aquarium Part I: Carbon Sources
http://reefkeeping.com/issues/2006-10/rhf/index.php

from it:

Species of macroalgae................Relative photosynthesis at pH 8.7 compared to pH 8.1 (as a %):
Chaetomorpha aerea....................75
Cladophora rupestris ....................100
Enteromorpha compressa.............. 67
Ulva rigida ................................... 100
Codium fragile ............................... 76
Asparagopsis armata....................45
Gelidium pusillum .........................33
Gelidium sesquipedale ..................18
Gymnogongrus sp. ......................39
Osmunda pinnatifida.................... 46
Porphyra leucosticta .................... 110
Fucus spiralis ................................ 86
Colpomenia sinuosa ....................100
Dictyota dichotoma ........................53
Cystoseira tamariscifolia ................57
Padina pavonia .............................. 53

[boxfishpooalot]

My theory is that the bacteria try and find any available source of sugar. And macroalgae is full of it. So the bacteria probably attack the macroalgae and suck out the availble sugars.

What color does it turn when its dead? White or brown.

[Randy Holmes-Farley]

Dead algae usually turns brown. Sporulated algae may turn white. :)

[jimsflies]

Thanks for the help!:)

When my caulerpa dies back it turns a grey green and once you touch it, it disintegrates.

[jimsflies]

I have tried iron in the past with no change. I should probably try it again since I have modified my fuge and seem to have generally better luck with macro since the modification.

[boxfishpooalot]

Well in my experience I have seen brown sloshy(goopy) macroalgae and white sloshy(goopy) macroalgae, both were dead. I have also seen sporulation which it turns white but retains its shape. Pulling it out is not goopy with sporulation. What a strange sentence :lol:

Fwiw my experience is macro algae are sensitive to:

Carbon sources and high alkalinity, also I believe macro does not do as good as it does in 12 hour lighting as opposed to 24 hour lighting. A rest period is essential for most macros. I have also noticed very slow stagnant flow causes sporualtion but not always the case.

When my caulerpa dies back it turns a grey green and once you touch it, it disintegrates

Imo this is dead and did not sporulate. Either high alk near them or a carbon source imo. :)

[jimsflies]

Your article is definitely a good discussion relative to my question.

Too bad you weren't able to get more info on caulerpa since its fairly common to the hobby.

I am currently running my fuge with continuous lighting. I have tried the reverse lighting cycle before and didn't notice too much...but my personal experimentation is less than scientific..often trying too many things at once to know what worked and what didn't. I think I will try the reverse cycle again to see how if that helps.

When you mention the kalk drip being upstream from the fuge...how far upstream is far enough? My kalk discharges into my tank drain pipe which goes through the sump and then a bypass loop off the return pump takes a portion of the water through the fuge. About the only further place upstream I could move it would be right into the display and I'm guessing that would create its own issues with a high pH area before its completely mixed?

I'm not currently using a Ca reactor. Is there any other option to enrich the CO2 upstream (or in the fuge)?

[Randy Holmes-Farley]

You method sounds OK. I mostly wouldn't dose directly into the water entering the refugium. More aeration in the sump could help. You could also manually dose soda water for a while and see it is helps.