What is a Freshwater Refugium?

What is a Freshwater Refugium?

Given the immense popularity
of refugia in the marine aquarium hobby, you might be left wondering if they
work in freshwater systems. While they haven’t quite caught on yet on the
freshwater side of things, they are just as applicable.

Freshwater refugia do indeed
serve the same purpose: Remove excess nutrients from the water (thereby
reducing unwanted algae growth) and support large populations of small
crustaceans (copepods, amphipods, ostracods, etc.). If there is any real
difference at all, it is in the type of “plant” used. Marine refugia rely
principally on macroalgae whereas freshwater refugia use mainly true plants.

There are so many aquatic
plants available that it is surprising that freshwater refugia aren’t more
widely used than their saltwater counterparts. Some types, though, are better
than others. Slow growers such as Cryptocoryne, for example, might not
be the best choice. Big, leafy, self-shading varieties like Anubias aren’t so great either. Mosses, worts and other tiny types of plant are just
too messy and difficult to contain properly.

Better types
include tall, fast-growing, deeply/densely rooting types that don’t mind living
in thick clusters. These are regularly harvested in sections (either clipped
back or pulled at the root) to allow for continuous growth. Thus, plants like Vallisneria, Stuckenia and Elodea work spectacularly.

Now, just
because a plant could work well in refugia doesn’t necessarily mean that
it will. For the high growth rates, you’d want in a refugium, you must
provide very intense lighting to support optimal photosynthesis. A mineral-rich
substrate can’t hurt, either!

Refugia are suitable for all types of freshwater
systems. Though it might seem counter-intuitive, they work really well on
planted systems. Why? Partly because they provide a huge, regular supply of pods,
which keep the leaves of plants in both tanks (main and refugium) clear of
detritus and fouling algae (fish in the main tank would eat all the pods
without a refugium!). Also, when maintained on a reverse light cycle, a planted
refugium helps to maintain a stable pH throughout the whole system, day and
night! For sure, refugia are destined to gain acceptance among both beginning
and advanced freshwater hobbyists.tr
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