Q re: '04 Kirby Adams article-Halimeda as export

[jgreen1025]

The rapid growth and calcification rates of Halimeda... indicates these algae could be every bit as effective as an instrument of nutrient export as the more popular Caulerpa. Regular harvesting of any algae will export nitrogen, phosphorus, and other organic compounds... After sporulation, the remaining Halimeda can be left in the aquarium, as they are essentially nothing but aragonite and can become part of the natural substrate.

I just found this article on halimeda yesterday. I've been trying to get my chaeto and gracillaria algae to grow better to export nutrients, but strangely without much success. All the while the halimeda has been growing like a weed! It never occurred to me that I had a great export medium in the halimeda, probably because it's also exporting calcium.

But the article has gotten me thinking - the "dead" leaves are a good aragonite substrate as mentioned above, and I often siphon them out of my tank into my refugium when cleaning. But since they're also good at taking up nitrates and phosphates, are those nutrients bound within the chlorophyll? If so, when the chlorophyll is expelled during sporulation it means those undesireable nutrients have been released back into the tank. But would that also mean that if I harvested some halimeda and allowed it to dry out and then crushed it up to add back to the refugium as substrate, those undesireable nutrients would still be in the leaves?

John

 

[Kirbster]

Hi John,

Nitrogen and phosphorus will primarily be in the living tissue of the Halimeda and not in the calcareous deposits. During sporulation, pretty much all the living mass of the algae is moved into the gametes and jetisoned - kind of like escape pods leaving a space ship the Klingons are about to blow up. That's why you're left with a fairly pure calcareous sand.

If you harvested living stalks and dried them, you'd have a bunch of dried tissue mixed in with the "sand". Any nutrients the algae took up would still be there and ready to be decomposed upon rehydration.

So I don't think Halimeda is a good choice for creating your own sand cheap at home. My point in the article was simply that there is no need to worry about removing the skeleton if it does die in the tank.

 

[jgreen1025]

That's what I figured, then. While I'm not too thrilled at such a good export method for calcium, at least it's a good way of exporting those nitrates and phosphates, so I'll keep my halimeda trimmed back regularly.

Thanks, and... uh... live long and prosper... or something like that!

John