Topic of the Month: Pros and Cons of Macroalgae in a Marine Aquarium

[MedicineMan]

We're all familiar with the nitrogen cycle: fish excrete proteinaceous waste which quickly breaks down into ammonia; the ammonia gets oxidized to nitrite then nitrate by bacteria living on our live rock, sand bed or bio balls. Ammonia and nitrite are toxic to animals, even in small amounts. The nitrate, however, is tolerable to most life in small levels (the exact level is controversial and beyond the scope of this discussion). But, left alone it will accumulate and become detrimental to the growth of our animals.

One of the great pros of macroalgae is that it actually absorbs nitrate and incorporates it into its own structure. As it grows, it incorporates more and more nitrate into itself. By harvesting the macroalgae from time to time, we're removing the end product of the nitrogen cycle-nitrate-from our aquarium.

Macroalgae can also add to the aesthetic value of our aquariums. We all want our aquariums to look nice and many of us try to get a natural appearance to them. Macroalgae is quite abundant in nature so it provides a certain visual realism to our aquariums we otherwise cannot achieve.

Many marine creatures live by eating macroalgae. It is, afterall, one of the lower rungs on the food chain! It also provides great cover for the tiny creatures many of our captive audience thrive on and allows them to colonize. For example, I kept a mandarin dragonette fat and happy in a 40 gallon aquarium because all the copepods and amphipods had great breeding grounds hiding in the masses of caulerpa I had growing.

So, we have nitrate removal, aesthetic appearance, free food and breeding grounds for more free food. What could be so bad about having macroalgae in an aquarium?

First, it grows. And no matter what we do, short of removing it, we can't train it not to grow over our corals. And, it can grow fast: I used to remove literally pounds every week or two! Not to mention it will grow under rock, attach itself to the rock and become a permanent fixture in the aquarium. It also can grow into pumps and cause failure by wrapping around the impellor and freezing the pump. This is why many people keep it in their sumps. Alas, not everyone uses a sump so that's not always an option.

Another problem is that, if it dies, it releases all that nitrate it had absorbed into the water column. The sudden rise of nitrate is probably more problematic than if the nitrate slowly built up over time. Thus, the sudden death-or, in the case of caulerpa, "going sexual"-results in a worse problem than if we never had the nitrate sink in the first place!

While macroalgae can provide many benefits to the aquarist, there are certain downfalls to its use. Keeping these in mind and preventing the potential problems, it can be a great benefit to most aquariums. One just needs to "stay on top of it", like all the other things in our little ecosystems.

Hopefully this little discussion will generate some more discussion. It is through communicating (exchanging ideas) that we learn.

[Scott 3560]

What are the best types to keep, isn't there a lot of different kinds.
I cant' seem to keep some types of it growing ?

[oyam123]

Is this the stuff?

my tangs eat it........

[MedicineMan]

Scott, there are many types. What I saw in the Rochester area that was readily available was Caulerpa. I've heard of some reef-keepers using Halimeda, which is common in the ocean here. However, if you have tangs you'd have trouble keeping it as they eat it like candy (unless, of course, you kept it in a sump).

[Ben]

Obviously, the situation depens on the nature of your tank. Anybody who wants to know the relative usefulness/nonusefulness of a particular alga can request me to look it up in my Marine Invertebrates book, which has a whole chapter on the pros and cons of different algae genuses.

Caulerpa is the speed demon. Put it in your tank and it will suck up massive amounts of nutrients, especially if you give it a more yellow light. Basically nothing else can soak up as much as quickly. However, it grows at a phenomenal rate and is a single celled organism that can get to several square kilometers in size in the wild (if not enough eats it). It is responsible for indescribable destruction where Pacific species have been released in new environments, choking corals and other photosynthetic creatures of all the light they need and releasing a chemical bath of yellowing agents and other things that make life rough for a reef. If you keep it, I'd personally recommend a sump with 24 hour lights and regular heavy pruning. Caulerpa only releases some of it's noxious chemicals at night, hence no night for it. Check it daily. If you see little "hairs" coming up from the surface of the "fronds", rip the whole thing out immediately. It's about to reproduce asexually.

Gracillaria is a free-floating algae sometimes called "tang heaven". It does decent nutrient uptake and is a great food for marine herbivores. However, you are not actually removing nutrients if you turn around and feed them back to your herbivores.

Chaetomorpha is the new "perfect solution" since people have realized that caulerpa wasn't. Chaetomorpha is a tougher free-floating algae genus that comes in several forms, but generally has fairly tightly packed strands of algae that make a great home for microfauna. It is probably one of the better nutrient exporters after Caulerpa, and it does not ever reproduce asexually and release all the nutrients back into the tank.

Halimeda is a great plant, but it is better for calcium control than nutrient control. This plant does not take up significant amounts of excess nutrients. It directly competes with stony corals for calcium that it pulls from the water to form its tough skeleton, but few herbivores will eat it away to nothing, so it is the one to put in a tank with a tank if you like the look of marine plants.

Please also note that most corals, especially lagoonal soft and LPS corals happily ingest nitrates. On a reef, they mostly take in trace amounts of ammonia as a supplemental food, because there is so little nitrate available. In a tank, nitrate is far more common and actually easier for them to ingest than ammonia, according to lab research I've read about. The issue is that it is not natural for them to have an excess of this food source and it may circumvent other normal biological processes.

[MedicineMan]

Thank you Ben. This is exactly what I was looking to accomplish with this particular idea!!

The question is, where does one obtain these?

A note about Halimeda in the wild. It grows quite ubiquitously here. One will be swimming over an apparently endless plain of it only to discover "holes" near rock outcroppings or other features that house reef fish. Near these there's about a 15 foot radius of clear sand bed where the fish have munched all the surrounding Halimeda!

[StellaMN]

Interesting about the softies/LPS way of nutrient export...

I have seen sumps full of pulsing xenia...that people used for their nutrient export. Although, I can't image how fast a tank could be decimated if the xenia crashed.

Chaeto sounds like a good way to go. I've had caulerpa go sexual in my tank...what a mess!!

J.

[oyam123]

what is the stuff in my photo???

is it safe?

[Ben]

Looks like a caulerpa. Lots of live rock comes with caulerpa, because the stuff is quite tough and willing to sacrifice 99% of its body to save 1%.

[oyam123]

so this is the stuff that is not safe?
should i pull it or keep it?
the tangs seem to eat most of it anyway.

[MedicineMan]

I should think since the tangs eat most of it you'll be OK. Caulerpa becomes a problem when it goes into asexual reproduction. I believe (but could be wrong) that keeping it in check (i.e. not letting it grow like wild) will prevent this.

[Ben]

Just look at it periodically. It can also yellow the water, so pull it out if you put a piece of white paper outside one end of the tank and it looks yellowish from the other end. Also make sure the tangs are eating some other types of algae, in addition to the caulerpa too. Too much caulerpa in the diet can be unhealthy.

[mjsandbe]

My experience with keeping macro algae in my sump has been very good. I feel it increases critter life, keeps algae out of the main tank, and helps with filtration. In my 58 gallon the only other filtration I have on the tank is a skimmer and it has been going steady for years.

I have two tanks. One with various algae in the sump, the other with none. The tank with the sump full of algae is generally algae free itself except for the sump. I have noticed great micro life in the algae mat. I dose iron and hack it apart on occasion to try and keep it from going sexual. The tank with no macro algae tends to have more cycling algae.

I am interested in Chaetomorpha, anyone in town have any? What does it look like?

Chaetomorpha is the new "perfect solution" since people have realized that caulerpa wasn't. Chaetomorpha is a tougher free-floating algae genus that comes in several forms, but generally has fairly tightly packed strands of algae that make a great home for microfauna. It is probably one of the better nutrient exporters after Caulerpa, and it does not ever reproduce asexually and release all the nutrients back into the tank.

[Ben]

I don't have any, but chaeto is a form of hair algae that either floats loose or grows on hard substrates. Some species look a lot like a brillo or steel wool pad with tight tangles of hair. Others look like... hair.

Also, mea culpa to gracillaria. I was just doing some re-reading and the experts consider it only slightly less powerful a nutrient export than chaeto. It also is dearly beloved of tangs and used in native Hawaiian cooking, so you don't have to just throw it away. I haven't found out if it has problems with going sexual at all, but it does not have the extreme problems of some other genuses. (While chaeto never goes at all.)

[pogodzib]

Originally Posted by mjsandbe

I am interested in Chaetomorpha, anyone in town have any?

I may be able to bring some with me the next time I'm over there.

Brian