caulerpa not growing

[andycook]

I would like more growth. What is the limiting factor

I have two kinds of caulerpa growing in my display tank. One is called sea cactus and the other was called split blade caulerpa by the seller. The sea cactus has been a steady grower. The other grew rapidly (almost fast enough to see it grow) over the course of a couple of weeks and then crashed. The few bits that survived have been really really slow to grow back. Dosing iron helped some but not much. I wanted to be able to harvest the caulerpa as a nutrient export.

Here is my tank:
65g tank with 20g sump
HOB filter for mechanical filtration
some kind of skimmer
running for nearly 2 years
bare bottom with boat board
2 175W 10K MH on a 10 hour light cycle
weekly 5g water changes with Reef Crystals
tank kept at 80. during the summer it got to 83.3 at the highest
2 clowns and one anemone. I feed frozen blood worms or clam or something
a small flowerpot with sand and sea grass
plenty of flow from 3 powerheads plus the return from the sump
1 to 3 snails.
RO DI water

water parameters at last test
sg 1.025
NH3 0
NO2 0
NO3 0
KH 8
PH 8.2
PO4 0.5 ppm
CAL 520

The live rock is old dead rock I had in a former tank that I kept dry for years. It is shedding gunk.

I also never see any coralline algae

Thanks for your help

 

[Subsea]

I will assume the Caulerpa is in the refugium. If it was growing like gang buster and it went sexual, you can assume with confidence that the limiting nutrient was used. I will assume that the macro that is still growing is more efficient at using the limiting nutrient.

Without more information, I would feed the tank and add iron in moderation. If you are using a skimmer, I would also add idione.

 

[andycook]

Thanks subsea. As I said in my post the caulerpa is in the display tank. What more information is needed?

 

[Khemul]

Cactus usually refers to Cupressoides. It isn't an extremely fast grower (at least by Caulerpa standards).

Split Blade... have any pictures? Usually Blade is Prolifera. Split Blade sounds like a description of a fern-type though. Either way, from the looks of it you hit nutrient starvation. They eat NO3 and PO4. You have phosphates, but lack nitrates. The rapid growers are known for stripping NO3 and then melting.

 

[andycook]

Here before the crash. I wish I had tank parameters from then. I suspect you are right Khemul.

 

[Saltliquid]

Here before the crash. I wish I had tank parameters from then. I suspect you are right Khemul.

I have an extremely rapid growing racemosa and it never goes sexual and I have chaeto and some of the taxifolia you have in that pic which I try to keep out by pulling it out and nothing ever suffers, the racemosa mainly controls my waters.
I found by precise testing that chaeto responds badly with new tanks bacterial imbalances and it likes to work on nitrate, but is fine with out it and my near completely natural main system does not allow any nitrate to show in a test.

Chaeto has a very different cellular structure and cyano content to caulerpa and is more closely related to blue green algae and caulerpa has its cyano with in its chloroplasts making it more so a phos remover.

These do great with average led lighting but not below 10 inches depth of water, I use a human vitamin supplement of iron from the health food store, iodine and all the components needed for corals, becuase algae needs calcium to grow.
There is more but one thing in particular, algae will suffer usually at temps above 25c, my racemosa dies at 26c,quite quickly!
You give them what they need and they give you a beautiful aquarium with no skimmer or water changes needed!