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Halimeda (cactus algae)

A typical Halimeda alga is a flexible string of flattened leaf-like structures often referred to as segments. Each segment is a deposit of calcium carbonate covered by the algal protoplasm and connected to its neighbors by a thin strand, giving the plant its flexibility. Some species, such as H. copiosa, take on the form of long necklaces, as if green disk-shaped...

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Searched Halimeda (cactus algae) in Reviews

Magic macro-algae for the sump-less that won't take over your tank

Comments

I keep a small amount and divide it up or remove it when it overgrows. In my experience only a few segments release at once creating no noticeable change in the water. While experiences differ from tank to tank, mine has been nothing but positive.

Needed to grow

Light
Nutrients
Calcium

Why is it magic?

Why I call it magic. It's a great nutrient absorber. Micro algae is an aquarist's worst nightmare. Especially for those who keep smaller tanks (under 50 gallons) micro algae can create a terrible mess. That's the stuff that grows all over your glass, and gets your nice white sand all gross. Even a small amount of Halimeda will out-compete the other algae and it will go away.

After setting up my 20 gallon tank I put in some reef stew in, which contains (among other things) algae, which is fine. Even though I put the recommended amount in it was too much and the tank went wild. It was to the point where I was scraping the glass daily! Finally I put a big clump of Halimeda in the tank and the very next day I did not have to scrape at all. Three days later and the tank and water are clear. It really was like magic.

Halimeda can be picked up at your local fish store much of the time. I've also found it at the PetCo. Generally it runs around $12.00 for a bunch. It grows quickly so generally speaking you get your money worth.

Liked about it

1. Very attractive
2. Quick growth rate
3. Most fish won't eat it. Even the fish that eat other kinds of algae don't seem to eat this because it tastes bitter to them. I don't know how they know, they just know.
3. Gamete release tends to be minimal.

Didn't like

1. Like caulerpa, Halimeda reproduces by releasing its gametes and cytoplasm into the water. Done en mass this can be dangerous to your tank, especially to fish. It tends to reduce the oxygen content in the water which of course can kill them. Tanks of larger size or those with very good aeration generally have nothing to worry about. I had it happen in a 5.5 gallon tank and all I lost was a peppermint shrimp. Everything else, including the fish, were fine.

I keep a small amount and divide it up or remove it when it overgrows. In my experience only a few segments release at once creating no noticeable change in the water. While experiences differ from tank to tank, mine has been nothing but positive.