Creating a coral bommie reef tank in a small cube aquarium

by Owen James

Bommies are outcrops of coral or rock on the natural reef

Bommies are outcrops of coral or rock on the natural reef

Regular readers may remember I’m considering setting up a couple of small reef aquariums, as a stop gap before I move house again.

One possibility I’m mulling over is a coral bommie-themed, hard coral dominated aquarium.

Coral bommies are outcrops of rock and coral. They emerge from flatter areas of coral and rock, or sit in sandy areas in the back reef.

I’ve an old 35-gallon Aqua Medic Chromis tank that I could use to create a small bommie-themed aquarium.

The idea would be to have a central pillar of rocks, completely exposed on all four sides to the current, with sessile lifeforms growing up and outwards from this central column.

This would be instead of the usual nano set-up, which is to cram the tank with rocks and coral due to the inevitable conflict between a small tank and greedy eyes at the Local Fish Store!

Bommie aquarium inspirations

I really admire a couple of gorgeous bommie-style aquariums on

Small tanks like this look far simpler to achieve than they really are, incidentally. In my experience it’s harder to keep a small tank ticking over than a large one, and it often seems almost as expensive!

In terms of the natural reefs, my library of coral books features a good few bommie pictures to inspire me, plus I’ve collected a few good images off the Internet via a Google image search for coral bommie pictures.

Inhabitants of the bommie aquarium

Corals and sessile invertebrates

Stony corals such as Acropora and Millepora growing up and out from the rock would dominate the aquascape.

Montipora and other encrusting or spreading corals could find a niche at lower levels, with certain compact (and non-invasive!) soft corals such as Zoanthids and Ricordea potentially tucked into the mix.

One or two Tridicna clams could find a home in the middle areas of the bommie, and I’d look to find a gap for a stand of a containable macro algae, too, such as the calcareous Halimeda, or maybe one of the red algae.

Keeping these animals in close proximity without too many turf wars would be a challenge.

Appropriate fish species

Photos of bommies always show very diverse fish populations.

  • Small wrasse would be ideal, but I’d need to select species that don’t require a deep sand bed.
  • Dottybacks and Anthias are frequently found in big shoals in this sort of environment, so they may be a good bet. The latter can be delicate, however.
  • Damsels would do well and feel at home, especially as the coral grew out to provide more real estate for them. On the other hand, the tank wouldn’t offer much territory for these notoriously pugnacious fish.
  • Clownfish would be fine, though I won’t be keeping anemones in this small tank. I’ve a soft spot for Sebae clownfish and haven’t kept them for years, so a pair would be high on my list.
  • Certain dwarf angelfish do well in smaller tanks, and might help with algae.
  • A goby or two could find niches, although some such as the Clown goby can pick at SPS.

In the wild bommies would be periodically grazed by passing tangs and surgeonfish, but I don’t think this tank is large enough to house one long-term.

Possibly if I came across a tiny regal or yellow tang I might add one, on the grounds I’ll be upgrading in future when I sort out my longer-term housing. If that plan was delayed, I’d pass the fish on. We’ll see.

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. A small group of cleaner shrimps could lurk within the bommie core, and they’d be likely to produce larvae every couple of weeks, providing some useful live food to the tank.

Tank environment considerations

  • The currents will need to be extremely fast and turbulent, preferably with a pulsed flow to send water surging across and around the central rocks.
  • Lighting will need to be bright and centrally located.
  • Calcium and other supplementation could initially be through two-part preparations. In the long-term I may need to add a calcium reactor or similar. But it might be avoidable in a small aquarium like this, even with the SPS growth.

I think I’d skip a sandbed in this tank; if I can move the water at the rate I’d like to then it will probably be blown about, although a slightly coarser bed is a possibility.

One reason I might add sand is that I don’t intend adding much live rock. With a lot of rock, the bommie effect is going to be diminished.

I’m currently thinking of hand selecting three or four pieces and placing them centrally, either secured to some supporting framework hidden within the rocks, or else sticking them together using an underwater epoxy. (Not great if I move house though!)

Much of the eventual structure and height will hopefully come from the growth of the hard corals.

In Part 2 I’ll look at the equipment issues for this bommie reef tank. Please do add any thoughts on this tank in the comments below, or subscribe to follow my coral bommie’s progress.

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