Ask the WWM Crew
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Imagine having all the resources, time and money to do
exactly as you please. What would you do? If you inherit or win the
lottery, give me a call. I'll be your personal dive-caddy,
accompanying you to all the places in the world where the water is warm
and clear. Yep, if I were independently wealthy, I'd go traveling,
diving the world's aquatic environments.
When most people picture entering the underwater world of tropical reefs, images of corals, rock, anemones and colorful fishes come to their minds. Is this realistic? Take a look around next time you're in the tropics, or at underwater pictures with an expansive view. Most of what's below the water is... water.
Taking a look at the living things, doesn't something seem amiss? I mean, compared with the land, are there more animals than plants? On closer inspection you'll find there is plenty of photosynthesis going on, and necessarily so. The phytoplankton suspended below the surface and throughout the lighted water column, and endosymbiotic algae are everywhere, and active metabolically. Less obvious in most cases, but still important are the sessile, or attached micro-colonial and macro-algae.
The strangeness of "why" there seem to be so relatively little "primary-producers" (photosynthetic plants, algae) compared with "consumers" (e.g. fishes and others) can be explained.
First I'll make a boring and shocking statement: Things are different in aquatic versus terrestrial systems! Boring because of course you know lots of ways their different. Shocking in the realization of how dynamic life on the reefs is.
It never fails to amuse me to read how "nutrient poor" tropical reefs are. Can you imagine the reasons for this? Obviously there is a tremendous amount of "fixed carbon" (i.e. living biomass) and flow of energy (everything eating and being eaten) going on; so why is the water considered "nutrient poor"? I'll tell you why; because those nutrients are jealously bound up by all the life around, and otherwise diluted by the oceans' volumes. They're not "nutrient poor", but nutrient "concentrated".
Look again at a reef, up close. What do you see? The algae there grow very quickly, but none look intact, or really vigorous. How come? They're continuously grazed upon. In experiments where algal feeding is restricted by fencing the area and removing algal predators, the algae take over the surface in short order.
What do you understand from the previous? Algae are a fast-growing, apparently important part of the natural reef. In a "balanced" setting their proliferation is kept in check by competition for scarce nutrient and perpetual grazing. Okay, me too.
This information can be of use to you in setting up and maintaining a marine system with more or less ease. Wouldn't it be great to strive for "a slice" of a real ocean environment in a captive system? Well, maybe not. Think about it; even if you had a humongous (let's say one thousand gallon) size tank, most of the space would be taken up by just the water, with actually very little rock, coral, and almost no macro-life at all. No, our captive seas are purposely over-crowded, hence over-fed/infused with nutrients, and therefore a struggle/challenge to keep balanced in our favor.
Even in such cramped, small quarters would growing some algae help? Decidedly yes. They aid in bio-filtering, removing/concentrating nutrients, making the same unavailable for undesirable forms of life, act as food and shelter, and hey, they look good.
Contrary to some reports macro-algae are not difficult to keep or culture. You don't need a tremendously sophisticated filtration system and a Doctorate in chemistry.
Most of the live algae you can buy are Greens (Division Chlorophyta), though most of what is stated here applies to all macro-algae species. The next Section on Brown (Division Phaeophyta) algae lists some techniques for collecting and mail ordering algae should you have no local source. Live algae can be easily be brought into a system by simply placing a small piece of "live-rock". The following expands on the benefits of macro-algae and lists their captive living requirements.
1) Bio-filtering: Macro-algae can aid considerably in establishing and stabilizing new or "out-of-whack" systems. They bring in and help to institute micro-organism communities, absorb nutrients introduced by food, decor and tap water. For systems with invertebrates, particularly anemones and live corals, live plant material can be especially helpful in improving water quality. In sufficient growing strength, macro-algae will remove nitrates, assist in buffering pH, uptake carbon dioxide producing oxygen, and assist in balancing trace elements (e.g. magnesium, phosphate, iron)
To some extent they are useful as bio-indicators; real-time monitors of the viability of the system. If your macro-algae will not live and grow, or start dying back, it is a warning sign that something is out of kilter chemically, physically and/or biologically.
2) Algae Control: Having a batch of algae intentionally growing in the system will go a long way in limiting the growth of unwanted forms (slime, string algae, fungus and bacteria) by competing for light, space and nutrients. For you reef-keepers, be aware that over-zealous algal growth may affect coral health through nutrient competition, smothering and possibly metabolite poisoning.
3) Food: Many, if not most of the marine fishes and invertebrates we keep augment their diets with large algae. What better deal than to have some continuously available for casual munching? Similar to our own nutrition, many trace nutrients make their way through this cycle.
4) Habitat/Ornament: macro-algae serve to break up the physical environment, affording hiding space from tank bullies and aquarists, and piece of mind to the inhabitants. Beyond this, they are aesthetically attractive; sheer beauty in terms of color, shape, size and motion.
For you folks with previous experience this will be very familiar turf. If pressed, you could write a parallel for using live aquarium plants in freshwater; so, what it takes to keep and grow marine algae are:
A) An established cycled, stable environment with "typical" conditions (high, steady pH; 1.021-1.025 specific gravity...) Synthetic water is fine. How can you tell when you're ready? Some of those "other" noisome micro-algae will have appeared on the scene.
B) Adequate nutrient levels; that probably do not require augmentation. You've been cautioned re the lack of need to replenish major and minor trace materials. Normal maintenance, including feeding should provide enough chemical nutrient. Adding more with metal halide lighting, carbon dioxide infusion, et al. might very
well boost growth, of macro- and micro-algae; with other, unwanted consequences.
Without adding any supplements, your algae won't die, it just will not grow as fast. Several of the authors in the bibliography below caution against too much macro-algae population and "pushing" these with additives. Algal metabolism can sway pH and other parameters, and even result in livestock loss.
You are warned again, concerning putting medications in your main system. Don't do it! Seek alternate treatment modes, dips, or best, a separate tank/system without algae or invertebrates.
C) Enough light, quality, quantity, and duration-wise. That is, balanced, full-spectrum, twelve plus hours per day, 2-4 watts per gallon. (please see Section 3) B) re lighting)
D) Being careful to limit mixing species of tangs, angels, butterflies, crabs, snails and others that relish destroying and devouring macro-algae.
E) Moderate, continuous water flow, stimulates growth and keeps debris off your algae.
Other Good/Useful Species:
In the trade are the true "old-timers" having been sold out of Florida since the fifties; that's 1950's, I'm not that old.
Genus Caulerpa by Bob Fenner, A closer look at Caulerpa - Common aquarium species and their care by Adam Jenkins,