[albert_dao]

http://reefkeeping.com/issues/2006-03/cj/index.php

As far as food goes, corals with small polyps eat, and there is no question about that. To reach the conclusion that feeding these corals is not important requires a reversion to the time before C.M. Yonge's studies in the 1930's on the Great Barrier Reef (or earlier), as well as complete ignorance of the past 75 years' worth of research. While it is true that some of these corals eat more than others, the species that are least reliant on food are not those that hobbyists believe are. In particular, study after study after study has found that corals such as Acropora are highly efficient predators, and that they eat large amounts of prey including a lot of zooplankton and particulate material every night in nature (Anthony, 1999; Anthony, 2000; Bongiorni et al., 2003; Bythell, 1988). Corals such as Porites cylindrica tend not to eat quite as much food as most corals, but they are the exception and not the rule (Anthony and Fabricius, 2000). They have merely circumvented the need for large amounts of food and can subsist on very little. Just to put some numbers on things, as aquarists tend to resist tooth and nail the idea that these corals eat things and need to be fed, Bythell (1988) found that Acropora palmata (the ultimate "SPS" coral) gets 70% of the nitrogen it needs for health, growth and reproduction from eating things such as zooplankton and particulates. These corals have to eat to be healthy! A recent study by Ferrier-Pages, et al. (2003) that was later confirmed by further testing found that corals that are fed grow their skeleton 30-75% faster, grow tissue 2-8 times faster, have more protein, have more chlorophyll and are in every way healthier and doing the things we want them to do faster than those that are not fed. Conversely, corals that are not fed suffer a precipitous drop in the amount of protein in their tissue and in their chlorophyll a concentration (Shick et al., 2005). A study by Sebens, et al. (1996) examined the differences in prey capture between two corals (Montastraea cavernosa and Madracis mirabilis). The Montastraea (relatively larger polyps) is known to catch a lot of food and to be very heterotrophic. The surprise is that the same sized colony of the Madracis (relatively smaller polyps) in a flume caught and ate 36 times as much food in the same span of time! Hmmm, seems to me like they need to be fed. Please do not take this information to mean that corals with small polyps need more food than corals with large polyps (let's not overcompensate now!), or you'll be missing the whole point. My intention is to illustrate that different species of corals show different food preferences, and that these preferences are not based on polyp size but rather on differences in each species' niches. It must also be noted, however, that a single species of coral can and will adapt to higher rates of heterotrophy or autotrophy depending on the conditions in which it grows (Anthony, 2000; Anthony and Fabricius, 2000). Corals often thought of as requiring bright light and little food can, and do, adapt in nature to conditions of low light with high food availability all the time.