Reefreaders

What Are They and Why in the World Would You Want One?

You’ve heard the word refugium or ‘fuge but do you really know what they are? According to Dictionary.com a refugium is “an area where special environmental circumstances have enabled a species or a community of species to survive after extinction in surrounding areas” and a refuge is “a place of shelter, protection, or safety. ”The refugiums on, or within, our aquariums perform precisely this function for our display tanks. In fact, refugiums have enhanced our ability to keep and even breed many species in our aquaria so greatly that Calfo and Fenner consider them important enough that they devote an entire chapter to the subject in their book Reef Invertebrates, An Essential Guide to Selection, Care and Compatibility.

Refugiums may be lighted or dark. Dark refugiums, such as the one described in the thread, can function as a food farm for your aquarium by allowing tiny critters, such as copepods and amphipods, to thrive. Many fish enjoy snacking on pods and others, such as most mandarins , rarely accept any other food. Whether your fish are pod snackers or obligate pod eaters, a refugium will keep a steady supply available

A lighted refugium provides a place to grow plants such as macro-algae, seagrasses and mangroves. Macro-algae and other plants function as water scrubbers, and when pruned or harvested, provide nutrient export thus helping to maintain good water quality in your aquarium. Additionally, fewer nutrients lessen the incidence of hair algae and other nuisance algae in your display tank. The two macro-algaes that marine aquarists are most familiar with are chaetomorpha and caulerpa although there are many other varieties, some of which are quite decorative. Pods flourish in macro-algae and it also serves a nursery for baby snails.

Have you ever noticed that the pH in your aquarium is lower in the morning before the lights turn on than it is in the evening with all the lights on? You can stabilize the pH by lighting your refugium on a reverse photo period from your tank. This means that when your tank lights are on the ‘fuge lights are off and vice-versa. When the lights are on, photosynthesis is occuring and carbon dioxide, which has a direct negative effect on pH, is taken up and pH tends to rise. However, when the lights are off, "normal" respiration from all those photosynthetic organisms produces carbon dioxide which causes pH to decrease. Using a reverse lit fuge will offset this effect by contining to consume the CO2 24 hours a day, thus, stabilizing the pH of the system.

Some macro-algae, particularily the green Caulerpa species, needs proper care to avoid having it “go sexual”, which is also known as sexual reproduction or sporulation. Having your macro algae go sexual can lower oxygen levels in your tank and create a toxic environment with sometimes disastrous results. Regular pruning is absolutely necessary to avoid sexual reproduction and has to be done at least weekly with some species. Many people who keep caulerpa believe that a 24 hour photo period will help prevent it going sexual. However, with this lighting shceme, macro such as cheato would fail to thrive.