Creating a patch reef habitat in a nano aquarium

by Owen James

I wrote recently about a small bommie-themed reef aquarium I’m thinking of setting up.

Bommies often occur in the semi-sandy, semi-rocky back reef areas known as patch reefs.

If I was setting up the larger tank my heart would love but my head resists (because I’ll very likely be moving house soon) then I’d definitely create a patch reef habitat.

One of the nicest tanks I’ve ever seen was basically a patch reef:

This patch reef tank did service as a frag nursery

This patch reef tank did service as a frag nursery

(More details here)

That tank is not exactly a looker, compared to the spectacular reefs you see winning Tank of the Month over at Reef Central.

But what I love about it is it’s naturalistic:

  • Loose groupings of assorted small corals
  • Little stands of macroalgae
  • Small amount of living rock placed directly into the sand

All these elements together evoke the No Man’s Land of a patch reef.

Here’s a real image to compare it with:

Two angelfish flit over a Caribbean patch reef

Two angelfish flit over a Caribbean patch reef

(Image from USGS)

The closest most of us come to this is if we set up a lagoonal-style aquarium, perhaps to keep LPS corals or certain soft corals.

Yet hard corals are just as well-suited to this habitat.

Certainly hard corals can grow perpendicular to a reef wall like in a typical reef tank, but if you were going to generalize you’d say they more often grow upwards from a horizontal plane, whether they be flattish table Acropora corals or massive boulders like Favia.

Forcing them to grow up and away from living rock like we often do in our aquariums isn’t exactly unnatural – coral can and does grow wherever it is able – but it’s not typical, either.

Setting up a patch reef tank

If I was setting up a patch reef aquarium, I’d want to use a six-foot or longer tank, with at least two-foot from front-to-back.

Live rock would be scattered on the surface of a sandy substrate, occasionally buried deeper into the fairly fine white sand, and rising in one or two places to form mini-bommies.

Tangs and similar fish would have an unusual amount of space to range over the rock and coral, since their movement would be unimpeded by the structures of a typical reef aquarium.

It would also be fairly easy to create currents in such a tank, again due to the lack of rock walls.

Unfortunately for me (but not for you, if you feel inspired and have a spare six-foot aquarium) I think it’d be a mistake to set up a large tank with a deep sandbed when I’m very likely to have to move house soon.

Could I create a patch reef effect in a smaller aquarium?

I’m not sure.

There are some nice examples of sand-based nanos floating around the Internet, such as the little 20-gallon tank below which I think is lovely:

This stunning nano is on the line between patch reef and grotto.

This stunning nano is on the line between patch reef and grotto.

(Full details here).

While the tiny Zoanthids and other corals scattered across the sandy bed evoke a messy patch reef habitat, there’s no doubt this little nano gets at least as much of its impact from the rocky wall towards the back of the tank (as well as the clever lighting).

I do think the undulating substrate and the choice of small specimens suggests it’s not impossible to create the illusion of a patch reef in a small tank.

But there’s a clear risk of it looking like a holding tank at your local fish store, if you lack the artistic vision of that reefer.

Possible inhabitants of a nano patch reef

Corals and sessile invertebrates

Almost any corals could be appropriate in a patch reef tank, since patch reefs frequently play home to all kinds of juvenile sessile invertebrates.

It’s through establishing a foothold in such places and putting down layers of growth that corals eventually build new reef areas.

In practical terms for our nano aquarium, smaller soft corals and hardier, more encrusting hard corals, as well as frags of LPS would be best.

Anything that grows big or quickly will soon throw the tank out of scale.

Appropriate fish species

Fish choice would unfortunately be limited by the size of the nano tank.

In particular the tangs, surgeonfish, butterflies, parrotfish and larger angels that would benefit so much from the open space of a patch reef aquarium would be completely ruled out on size grounds.

Equally, many of the fish that are best suited to life in smaller aquaria also feel most at home in dense rocky environments – they don’t wander far, which is what makes them suitable for small tanks, but they also like a complicated territory to feel secure.

Small Centropyge angels are one species that would not be suitable for this reason.

The best choice might be one or two small gobies, and perhaps a few Chromis damsels.

Neither fish will add much ecologically to the tank – they won’t graze algae, for instance – but they will fulfil an aesthetic function.

Other invertebrates

Reef snails like Astrea would be definite additions to the tank. I’d probably add a small hermit or two, for all their foibles.

Plant life

Although not a full-on lagoonal habitat, patch reefs often feature stands of macro algae, and I’d look to include some slower-growing types in any patch reef habitat.

Environmental factors and equipment

The environmental requirements and equipment needed would be very similar to that detailed for the coral bommie aquarium earlier, so refer back to that post for more information.

Bommies are often located in patch reefs.

In terms of flow, you could probably get away with less powerful pumps, especially while the tank was relatively young, as there would be a very clear run for the water without coral or rock structures to push back.

A sandbed is surely a must for a patch reef tank, not least for aesthetics, which will present some constraints to the current, also.

In terms of lighting the patch reef, a longer shallow tank could use less intensive lighting.

T5s would do the trick in sufficient numbers. For a nano tank patch reef, I’d even consider trying out LED strips.

There are many ways to filter such a tank, but again there would be no need to do anything very different from the bommie nano tank.

Using algae / mud-based filtration and encouraging an extensive sandbed fauna would be an option, but it wouldn’t be as compelling as if you were creating a lagoonal habitat with eelgrass, mangroves, filter-feeders and seahorses, say.

Final thoughts on the nano patch reef

I’m not finding this idea as compelling as the nano bommie tank.

I’d love to set up a long, flat and shallow tank without live rock walls, but as I said above I’d hope to enjoy algae-eating herbivores such as tangs gliding above it.

In a nano tank, the sense of scale would be lost, while the growth of most specimens would soon give the appearance more of a grotto.

I think a 48×18x18” tank is the minimum size to attempt a patch reef habitat, and ideally it’d be a couple of feet longer.

For me, that must wait until I’m in a more permanent home, but please let me know if you’ve taken this biotype further in the comments below!

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{ 1 comment… read it below or add one }

logan 03.26.09 at 5:28 pm

I think a patch reef could look too ‘messy’ in a nano. I definitely agree that a longer and wider tank would be best suited for it. There was a really great tank with a sort of mix of macro algaes and photosynthetic gorgonians done just like you described, I’ll have to see if I kept the bookmark……

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