The refugium revisited?

I received an email from a customer the other day that sort of triggered a recollection of a "thing" I was working through over the past few months..

He was talking about an interesting diversity of life forms he was seeing in his aquarium after a few months of operation with a variety of botanicals. This reminded me of some thoughts I had about both the potential biodiversity within the botanical aquarium itself, as well as the possibility of creating a "botanical refugium" of sorts to foster said biodiversity!

Now, the idea of a "refugium" is not at all new to the reef aquarium world, although you see less of them these days than you did in the early 2000's..a shame, because their benefits are numerous. Yet the idea has been little discussed in the context of freshwater, other than a scant mention or two in Discus discussion groups that I've stumbled on. Essentially, a refugium is a dedicated space (typically a vessel separate from the aquarium), which performs multiple functions to support the display aquarium it's associated with.

These include nutrient processing via plant or macro algae growth, or organisms such as worms, copepods, etc. which consume uneaten food and act upon organics (nutrient export). A refugium, as its name implies, provides a "safe haven" for life forms which would otherwise be consumed by the resident fishes in the display aquarium. And, these animals will often reproduce, and some of them are swept into the main aquarium, providing a natural food source. Typically, a reef refugium employs live rock and sand, as well as macro algae. Being essentially another aquarium, a refugium also adds to the stability of your display by adding overall capacity to the system, and can provide additional circulation and oxygenation.

Now, in a blackwater, botanical-style system, I can think of a number of cool uses for a refugium, playing on the theme above, but thinking it through a bit further.

A refugium could be used as THE source of botanicals for the display aquarium in situations where you're, I dunno- weird- and don't like the aesthetics of decomposing leaves and botanicals in your display, but dig the blackwater and other benefits. You could throw all of your pods, leaves, and other stuff into the refugium, and let them do their thing, influencing the environment in the main aquarium.

You could also use it for keeping some specialty fishes which might otherwise be lost in the main display. For example, if you like small "Darter Characins" which live among the leaves, and would be lost or in danger in your 120-gallon cichlid display, a refugium could provide the perfect place for you to keep them. Or to keep Neocaridina shrimp, which would otherwise be a part of someone's meal plan...

Or as a nursery of sorts for Apisto fry, killies, etc. Kind of like a built-in excuse to get another tank, under the guise of it being a "piece of support equipment" for your main display. Genius!

And of course, you could grow live plants in there! Yeah, let's suppose that you like live plants and want to grow them in your blackwater tank, but you keep a group of rowdy cichlids..or other fishes which refer the diffused lighting found in blackwater habitats- conditions that make keeping some of the high light-loving plants a sketchy proposition. So, you set up your inline refugium just like a typical planted display tank, with rich substrate...and light the crap out of it with LED, T5...hell, even metal halide, and run it on a "reverse daylight" schedule, so that the plants are producing oxygen during the aquarium's "dark" period. Or, you could just be "conventional"  and simply run it on the same lighting schedule as the display...

And the whole "food culture" idea utilizing a refugium is awesome to me! I mean, you could grow Daphnia, copepods, worms...all sorts of aquatic crustaceans that are tasty supplements to your fish's diets. And, with an abidance of botanical materials present, they will reproduce rapidly.

I noticed this as an incidental thing in my awesome top-off reservoir made by my reefing buddy Marc Levenson of Melev's Reef (shameless plug)... I keep some catappa/guava leaves in there, as well as a few other botanicals, to sort of keep the "tint" going in my topoff water. And a few months back, I tossed in- on whim- a small starter culture of Daphnia, just to see how it would go.  Well, when you shine a light in there, you can see a whole bunch of 'em swimming around! And a few of them no doubt get drawn into the little pump which meters some water to the display as it evaporates, providing my voracious characins the occasional surprise treat.

Sort of an "auto feeder", if you will! And of course, if you actually incorporate a legit refugium into your system for the purpose of cultivating supplemental food organisms, you could either harvest directly with a net, or allow some of the creatures to be swept up into the pump and distributed into the aquarium incidentally.

Could it be possible to create a large and populous enough refugium to provide all of the food for your fishes, without the need for supplemental feeding? Crazy-cool experiment, right? I'm sure there is a "tank-to refugium" ratio that someone figured out to make that work..or not. But a cool thought and interesting experimental project for the intrepid botanical/blackwater aquarist!

Are the wheels spinning in your head yet?

Yeah. I'm getting excited just writing about this!

Oh, and we've talked repeatedly here about the concept that a botanical/blackwater system itself, with the decomposing leaves, botanicals, biofilms, algae, etc. is essentially a very good mimic of nature, with a surprising amount of biodiversity present. So, you could really forgo the idea of a dedicated refugium and just stock the hell out of your display with leaves and botanicals and enjoy many aspects the aforementioned vessel..It's simply one of the many collateral benefits of running a botanical system. 

I think it would be a really cool idea to revisit the concept of a refugium, and incorporate it into your blackwater/botanical system. The discoveries, benefits, and just plain enjoyment from creating another little world within your system is ultra-compelling, huh?

Until next time...

Stay creative. Stay daring. Stay engaged. Stay "geeky!"

And Stay Wet.

Scott Fellman

Tannin Aquatics 

Scott Fellman
Scott Fellman


2 Responses

Scott Fellman
Scott Fellman

January 08, 2017

Absolutely, Carmickle. The possibilities are really endless, in terms of creating systems with utility, biodiversity, food production, and benefits we haven’t even thought of! Terre is a TON of information out there on the ’net about saltwater refugiums, and one could easily extrapolate plenty of useful stuff about their design, implementation, and operation, and apply them to FW. Enjoy!

carmickle forster
carmickle forster

January 08, 2017

I’ve been thinking about hooking multiple tanks together with filters but this is a new idea that i want to look into more. Do u think this would work with tropical fresh water tanks as well. Thanks

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