No one ever said that keeping reef aquaria is totally uncomplicated. Especially keeping them clean! Sure, some maintenance approaches are simpler than others; natural methods are, for example, fairly effortless means to control nuisance algae, detritus and pests.
Natural methods certainly require some research, planning and occasional monitoring; but for the most part, they involve adding organisms that improve environmental conditions simply by doing what they do… naturally. For you, this eliminates much need for tinkering with touchy equipment, changing expensive chemical filtrants, constantly algae wiping, etc. Plus, successfully creating a dynamic, self-sustaining ecosystem is hugely satisfying.
Perhaps the most common and most important agents of biocontrol for both algae and detritus are copepods. This should make plenty of sense, since these tiny crustaceans fulfill the same ecological role in most natural aquatic/marine environments. Increasingly, aquarists are taking all kinds of measures (e.g. phyto dosing) to ensure that their systems can sustain large copepod populations. Arguably, the surest way to promote high copepod density is to install a planted refugium.
Planted refugia (specifically the macroalgal “plants”) already have other, well-known benefits; they reduce dissolved nutrient concentrations, for example. These are considerable benefits, for sure. But planted refugia are worthwhile for their pod-promoting properties alone.
So–by cranking up pod numbers, a refugium helps to keep a tank clean. That doesn’t mean that the ‘fuge itself can’t get dirty. For example, massive accumulations of detritus can form in densely planted refugia. And pods can’t control pests. Like in the main tank, the best way to tackle refugium cleaning and remove pests is to adopt natural methods.
But planted refugia are necessarily different environments from the main tank. This means that many animals used for clean-up in the main tank cannot be used in the refugium. For example, urchins are excellent algivores that are great for the display, but can’t be in the ‘fuge because they’d eat all of the macros! There are just as many species that are safe with macros, but aquarists just don’t think to put them in the ‘fuge. Imagine what happens if you put a gazillion aiptasia-eating animals in the main tank but stock none in the refugium–you’ll probably never get rid of the aiptasia, right?
Again, overall, a refugium makes it easier to maintain a clean, healthy reef tank. But your tank will be even cleaner, with even less effort, if the ‘fuge houses its own clean-up crew.
Obviously, planted refugia are brightly illuminated environments. Thus, even in such close proximity to their macroalgal competitors, nuisance microalgae can take hold there. It can grow on the glass, on the sand or even on the macros. A well-rounded group of algivores can control these bad algae. This must, however, not include any animals that might develop a strong taste for your macroalgae. Sure, some snails might eat some soft macros like Ulva, but it’s all good so long as they focus on the microalgae.
There are a few captive-bred snails that are suitable for this purpose. Not only are captive-bred trochus snails and siphonaria limpets both excellent algae-eaters but they also are much hardier than wild-collected specimens.
Particulate organic matter (POM) is highly prone to settling out in refugia (especially planted refugia) where flow is reduced and certain macros (especially meshy types like Chaetomorpha) act like mechanical filters. This isn’t necessarily bad. For one, it removes these solid wastes from the display tank, where they would otherwise be much unsightlier. Also, by settling POM in the refugium, it is concentrated in just the spot where most of the pods are (i.e. where they can eat it most efficiently!).
Still, in tanks with lots of well-fed fish, detritus can build up faster than the pods can consume it. This is where the pods can use some help. Detritivorous snails are perfect for this job. Again, because wild snails can be touchy, captive-bred specimens are a much better choice. Thankfully, the sludge-busting cerith snail and nassarius snail clean up crews are available as captive-bred. Tiny burrowing snails such as these significantly improve the appearance and water quality of a reef tank, and indeed refugium, by consuming organic wastes. Most of these also contribute to some film algae control as well.
Many small invertebrate animals are used to control pests of various sorts. Most of these are quite happy to live in the ‘fuge. The list of pest control critters is a bit long to run through in its entirety here, but we’ll posit the peppermint shrimp as a great example. This is, for sure, due to its proven usefulness in eradicating a common and particularly nasty pest, the aiptasia anemone. But these shrimps are also pretty good at scavenging wastes in general. This would include larger chunks of organic matter such as fish food that might find its way into the ‘fuge. These guys can mop up in seconds what would take copepods hours to do. This is especially important when snails die in the ‘fuge; a peppermint shrimp will eat a dead snail long before it has a chance to decay and foul the water.
Your refugium clean-up crew may be built around your specific needs and specific type of system you have. But regardless of the details, it’s a really good idea to remember the ‘fuge when your stocking critters for algae, detritus and pest control. This undoubtedly will simplify your maintenance regimen and reduce your reliance on complicated, expensive filtration technologies. And of course your tank will be a whole lot more interesting to observe!