Does anyone have experience with alge scrubbers

Does anyone have experience with algae scrubbers?

I am in the planning stages of setting up a saltwater tank and am curious about algae scrubbers.

Various links are found when searching with Google but is there local experience out there?

Cheers

I've never had any personal experience with them but have also never heard any good things about them. Most people tend to use a refugium instead to achieve similar results to what an algae scrubber achieves only with much better end results.

Thanks Frosty,

But I like the idea of a algae scrubber, the idea of skimming to remove waste also starves the tank.... as I am reading ....

Taken from "Reef Food" by Eric Borneman:
http://www.reefkeeping.com/issues/2002-07/eb/index.php

"Detritus, marine snow, particulate organic material, and suspended particulate matter are all names for the bits of "dirt" [food] that flow around the reef; material that is composed of fecal material, borings, algae, plant material, mucus, associated bacteria, cyanobacteria and other particles. Decomposers (mainly bacteria and associated flora and fauna) break down waste material in the water, on the reef, and primarily, in the soft sediments. The result of their presence and action is not only a food source in and of itself, but provides raw material for channeling back into the food chain, largely through the benthic algae and phytoplankton.

"Phytoplankton [food] are small unicellular algae, or protists, that drift in the water column. They may be very abundant in and around coral reefs, and they are capable of absorbing large amounts of organic and inorganic nutrients. [...] Some of the reef animals can feed directly on phytoplankton; many soft corals, some sponges, almost all clams, feather-duster worms, and other filter feeders utilize phytoplankton directly as a food source. Small animals in the water column, termed zooplankton [food], also utilize phytoplankton as a food source. For the smaller zooplankton, phytoplankton and bacteria are the primary food source.

"Both of the [photos not shown] are from reefs on the Great Barrier Reef, Australia. The left photo shows the clear "nutrient poor" (oligotrophic) waters of the outer reefs. The right photo is of an inshore "nutrient rich" lagoon reef off Townsville. Notice how coral coverage in both systems is high, and even though the green phytoplankton-filled lagoonal reef is nutrient rich, it supports a high density of Acropora.

"Coral reef food sources, then, are largely produced by the ocean. Bacteria, detritus, phytoplankton, zooplankton, small benthic fauna, mucus, and dissolved organic and inorganic material of various types and sizes are what comprise the majority of food on a coral reef.

"In aquaria, we are faced with several realities. Our phytoplankton and zooplankton populations are generally negligible to non-existent in comparison with coral reef communities. Those which do exist are either rapidly consumed without having a chance to reproduce, or they are rapidly removed or killed by pumps and filtering devices or suspension-feeders. Coral mucus, bacteria, detritus, larval benthos and other "psuedo-plankton" might be present in a reasonable amount if the water column were not stripped. On the other hand, dissolved organic and inorganic material [nitrate, phosphate] levels are frequently much higher than they are in the ocean. [...] Even very well maintained aquaria are generally found with much higher levels of nitrogen and phosphorous than wild communities. Even though many desirable organisms are able to utilize these nutrients, levels in most aquaria are very unnatural, and coral reefs under such conditions often wane or die - a process known as eutrophication.

"It is the lack of water column-based food that results in limited success with the maintenance of some desirable animals, such as crinoids, flame scallops, clams, certain corals, sponges, bryozoans, and many other invertebrates. Even the symbiotic (zooxanthellate) corals [like SPS] suffer, despite many obvious long-term successes with these animals.

"In terms of previously mentioned export mechanisms, it really does little good to be cultivating or adding more food material in the water column if it is all being rapidly removed by filtration devices. Live rock and sand provide abundant filtration, and some of the articles in past issues describing the set-up and use of unskimmed tanks are, in my experience, something that should be seriously considered. Algae Turf Scrubbers are also viable systems that provide low ambient water nutrient levels [of nitrate and phosphate] while maintaining higher amounts of food and particulate matter in the water. I also feel that if protein skimmers are used, they should probably be used in an intermittent fashion.

"Phytoplankton are the major source of primary [food] production in the ocean, and one of the most important driving forces of global ecology. In fact, phytoplankton production influences all life, by being at the lowest rings of the food chain.

"The reason [phytoplankton] are so important on a regional or global scale is simply by virtue of the fact that the upper 200 [meters] of oceanic waters is filled with phytoplankton and covers over 70% of the earth's surface.

"What eats phytoplankton? In the water column, zooplankton [food] are without question the primary consumers of phytoplankton. Zooplankton grazers vary according the area and the time of year, but include primarily ciliates, copepods, amphipods, and tintinnids.

"Stony corals are generally not well adapted to the sieve or filter type feeding that characterizes the soft corals (Fabricius et al. 1995, 1998). They are, however, well suited to the capture of zooplankton prey.

"It is of paramount importance to recognize that the biomass of potential grazers [which need food] in an aquarium is many times what it would be in the same volume of water or surface area as the bottom of oceans or on reefs, and also, that the availability of water column borne food is many times greater in the ocean than in an aquarium.

"Perhaps most importantly, is the almost ubiquitous interaction between bacteria and phytoplankton. Phytoplankton release dissolved organic substances, and bacteria utilize them as nutrient sources. Most phytoplankton cells, especially large ones, are coupled nearly continuously with coatings of bacteria [which are consuming the dissolved organic substances].

"The amounts of phytoplankton present in reef aquariums are not known but are probably considerable. However, they are also probably rapidly removed by grazing and export devices [skimmers].

"Copepods comprise by far the largest fraction of total zooplankton - more than all the other groups combined.

"Zooxanthellate corals (many diverse species) could survive "indefinitely" if provided with adequate zooplankton, even if totally deprived of light. In contrast, corals provided light and deprived of zooplankton did not survive.

"One of the greatest myths among reefkeepers is that "SPS" corals depend mostly on light, and require less food than "LPS" corals. This is entirely untrue. As an example, consider the data from [pic not shown]. This graph shows the capture rate of an equivalent biomass of two corals, the large-polyped Montastraea cavernosa and the very small-polyped Madracis mirabilis. For those unfamiliar with Madracis, it is related to and somewhat resembles Pocillopora and Stylophora. The capture rate of the small polyped coral was 36 times greater than the large-polyped coral! Furthermore, M. cavernosa has been shown in other studies to be a voracious zooplanktivore.

"Many other studies confirm the predatory [feeding] abilities and requirements of "SPS" corals. It should not be surprising, given the fast growth rate and fecundity of many small polyped species. In other words, more growth and reproduction requires more energy, especially nitrogen for tissue growth. The difference, if one exists between "SPS" and "LPS" corals, lies primarily in the size of the food captured. Most of the prey of small polyped corals may just be too small to see. Aquarists have a tendency to be strongly visual, and so if gross observations don't indicate that a coral is consuming food offered to it, they wrongfully assume the coral must not need to be fed.

"Some species rely more on zooplankton than others, and if anything, the "SPS" corals feed on zooplankton a lot. In fact, most corals show linear feeding saturation dynamics under all but extremely high particle concentrations. What this means is that corals have a hard time "getting full." They continue to capture prey, and do not get satiated until prey densities become so great that such levels are almost never possible. To put it another way, even if you were to pour a pound of food per day into an average sized reef aquarium, the corals would still "be hungry."

"In a September 2002 coral reef conference in Cambridge, several papers were presented that should give an idea of not only the very latest information, but also emphasize what is written above.

"Many years ago, one of the only [food studies] for a coral was done for what might be considered the ultimate shallow-water "SPS" coral, Acropora palmata (Bythell 1988, 1990). The study showed, basically, that 70% of this coral's nitrogen needs were met by feeding, and that 91% of its carbon needs were met by light. [In 2002] three more corals, the larger polyped Montastraea cavernosa, M. annularis and Menadrina meandrites [were studied, and the researchers found] zooplankton to provide 20-80 times the carbon and 112-460 times the nitrogen previously shown for Acropora palmata. Finally [in 2002, researchers studied] the role of zooplankton consumption on the metabolism of the small-polyped coral, Stylophora pistillata under 3 different conditions of light (80, 200, 300 µmoles m-2 s-1) and 2 feeding regimes (Artemia and natural plankton). They found that regardless of light, fed corals had higher chlorophyll-A concentrations, higher protein levels, and had photosynthesis rates 2-10 times higher than those deprived of food. This group also measured calcification rates, both in the dark and in light, and found that calcification, as is well known to be the case, is enhanced by light. However, for the first time it was shown that feeding results in calcification rates 50-75% higher than in control corals (not fed). It was also found that feeding does not affect the light-enhancement process of photosynthesis on calcification. To make these results completely understandable, if corals can feed on zooplankton, they will calcify 50-75% faster irrespective of light levels provided.

"Of all the many things that can potentially increase respiration, photosynthesis, and calcification -- and have been shown again and again to do so absolutely -- feeding and water flow are the major players. Light, of course, is critically important as well, but aquarists by and large can and do provide enough quantity and quality of light for corals. Period. Phytoplankton, while a very beneficial addition to aquaria, does not feed most corals (Borneman 2002). Something as significant as zooplankton to both coral and coral reefs would seem worthy of the highest efforts in trying to produce, add, grow, substitute or in some way provide to tanks. I cannot think of a single greater accomplishment and advance for aquarists than to provide by whatever means (higher export and higher input, larger refugia, purchase, plankton tow, culture, etc.) significantly greater levels of zooplankton or zooplankton substitutes to their corals. I hope I am being dramatic enough by writing this, for this is among the most important steps that must be made to realize the majority of those lofty goals and ideals that are so often stated and desired by those keeping corals in aquariums.

Skimmers remove zooplankton; Scrubbers add zooplankton seems to be the general theme here.