Acan Lord Husbandry (5 min read) — How to Keep Your Rainbow Acan Colourful (Aussie vs Indo Rainbow Acans)

Our first batch of aquacultured rainbow acans sold out far faster than we expected — thank you all for the support.

Since then my inbox has been full of questions about acclimation, colour morphing, and how to stop these losing their rainbow. That made me realise something: after the coral import ban, rainbow acans effectively vanished from the UK market for years, and a lot of people simply haven't had the chance to keep one. So as the second batch goes live, I want to put together a short guide.

The basics (easier than you think)

I won't spend long here. Acan lords want mild flow, and additional spot feeding will noticeably speed up growth on these meaty LPS — we use Reef Roids + oyster eggs + phytoplankton, 1–2 times a week.

On parameters, they're genuinely undemanding. The two situations that will actually cause you problems are phosphate going off the scale (which very easily leads to secondary bacterial infection) and calcium dropping too low (the polyp will start to lift away from the skeleton). But in either case, other corals in your tank will have started dying long before the acan lord does. Overall, this is an easy-level, hardy coral.

So what should you actually worry about? (colour, not survival)

Unlike torches, you're unlikely to accidentally kill an acan lord. The question I get asked most is the other one: there are a lot of rumours that acan lords colour morph — will mine keep its rainbow in my tank?

The first thing to understand is that "colour morph" covers two completely different things.

The first type happens to wild collected strains as they're brought from the reef into a home aquarium and domesticated. They lose some of their colour along the way, the mechanism isn't well understood, and the change is permanent and irreversible.

The second type is the same thing that happens to any other coral: in less-than-ideal tank conditions, the colour shifts — yellow turning to orange or red, for example. On the existing heads this is also "permanent", but unlike the first type, once you correct the cause, new heads will grow back in full rainbow colour.

If you're buying aquacultured acans from us, the first type isn't something you need to think about. And the second type is almost entirely avoidable with correct light acclimation.

Aussie vs Indo (not just a lineage label)

Most people know rainbow acans come in Aussie and Indo strains. What fewer people realise is that beyond lineage, these two behave differently in the tank — and the most significant difference is how much light they want.

The standard understanding of acan lord is: low light, bottom of the tank, meaty LPS. So what if I told you that you can place them in the middle-to-upper third of your tank, at 250–300 PAR — close to SPS territory — and they'll actually grow richer, brighter colours?

(A typical Indo rainbow strain)

For Indo acans, the low-light instinct is correct ✅. In fact, light that is too strong too early is the main reason their yellows turn orange or red. For a freshly arrived acan lord, we suggest leaving it at around 50 PAR for at least a week, then moving it gradually to a brighter area, with a final target of no more than 120–150 PAR (in a low-nutrient system, their light tolerance is lower still).

The acan in this photo is actually getting too little light — somewhere around 20–30 PAR — which is why you can see it "long stemming", the same reaching-for-light behaviour zoas show in dim spots.

(Note the purple flesh in this photo — freshly fragged acans colour morph more easily, so this is a deliberate better-safe-than-sorry temporary measure.)

The Aussie strains (higher light, and two different endpoints)

Aussie strains need the same patient, weeks-long acclimation — rush it and they'll bleach. But their end goal is different: they need stronger light to hold their colour, and under-lighting them will cause colour morph rather than prevent it.

Here's the nuanced part. Aussie rainbows actually show up in two distinct expressions. 

In the first photo, the yellow in this Aussie rainbow develops from a red/orange base, much like the Indo rainbows — so when light is insufficient, it falls back towards a dusky red/orange.

In the second photo, the yellow develops from a green base instead, so its colour morph reverts to green. This green-based version is unique to the Aussie strains, and personally, I've found this type of strain has the potential to be the brightest of all the rainbow acans.

This same green-base-to-yellow development is also a distinctive trait of some Australian Acan bowerbanki strains. The photo below shows one of the show-grade Aussie Bowerbanki colonies we propagate here at Zoanation.

The 2 rainbow strains pictured above originated from hand-picked Australian coral farm specimens selected years ago. These lineages have since been propagated and passed down in our tank.

For clarity, we've now labelled the Aussie strains in our listings, so you'll know which lighting approach to follow before your coral arrives.

Thanks for reading, and we hope this helps your rainbow acans settle in, colour up, and grow.

Dr. Chen

Zoanation