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HOW TO CARE FOR YOUR SUN CORAL
Tubastraea Coral Care
Sun corals of the Genus Tubastraea get their name from their bright yellow coloration and sun-like appearance of each polyp. Despite their bright sunny name, these corals are non-photosynthetic which means they do not get any energy from the light. In fact, they are probably the most well-known non-photosynthetic coral in the hobby. Their popularity is rooted both in their beautiful appearance as well as the challenge to keep them alive and thriving.
The challenge of keeping Tubastraea, or any non-photosynthetic coral for that matter, is keeping it properly fed. Often times, hobbyists grossly underestimate the amount of food is necessary to keep these corals alive. The result is the coral slowly starves. Over time the sun coral opens up less and less for feeding, ultimately leading to its death. Luckily, of all the non-photosynthetic corals in the hobby, Tubastraea are some of the most aggressive feeders that can be fed a wide array of meaty foods. There are similar non-photosynthetic corals to Tubastraea such as Balanophyllia and Dendrophyllia with roughly the same care requirements. The black variety of Dendrophyllia can be a little more difficult to get eating but it too can be kept once it starts feeding regularly.
Location
Tubastraea are found all over the tropical waters of the Pacific. In particular, they are regularly harvested from the islands of the Indo-Pacific including Fiji, Tonga, Solomon Islands, and the Great Barrier Reef.
Lighting
As mentioned above, Tubastraea are non-photosynthetic. Because Tubastraea are non-photosynthetic, they can theoretically be kept in an aquarium with no lighting at all. In the wild you often see them in deeper water or on the underside of caves. In the home aquarium one could simulate this by placing the sun corals in caves or under overhangs, but such placement makes it difficult to view them or feed them.
On the other hand, I would not keep them under bright light because I think it is still possible to burn them up under extremely intense lighting. As a general rule I would keep them under 75 PAR to be safe.
Low Light
Low light translates to about 30-50 PAR
Medium Light
Medium Light is between 50-150 PAR
High Light
High Light is anything over 150 PAR
Although the coral won’t get much in the way of nutrition directly from the tank’s lighting, the kind of light provided will make a big difference on the appearance of the coral. Sun corals do not fluoresce under actinic lighting. To best showcase their appearance, I like to keep them under daylight colored lighting to complement their bright yellow color. This is my personal preference and that is not to say that this coral under blue lighting looks bad, it just gives it a more muted aesthetic.
Lighting is a loaded topic, so for a more in-depth discussion of lighting, please check out our Blog all about Lighting or see our detailed lighting video below.
Water Flow
Tubastraea are not reliant on strong flow and in fact, lower flow is helpful during feeding to give the sun corals an opportunity to catch the food out of the water column.
The best trick I learned is to place sun corals a few inches below a powerhead. This provides the coral with some shade from the light but more importantly puts the colony into a swirling flow area. The next time you feed your aquarium, spray some food around the powerhead and look at the area just below the pump. A lot of times I see a flow pattern where the food circulates several times before getting sent across the tank.
This effectiveness of this trick depends a lot on your tank dimensions and the kind of pumps you are using. In shallow tanks, the colony can be placed on the substrate or low rock work and benefit from this flow pattern but in deeper tanks, not so much. A second trick I learned was to take old algae magnet scrubbers and glue the colony onto the wet side magnet and then place it under the powerhead. You can also do this with magnetic frag racks.
Feeding
Feeding has been a recurring theme through this whole article but I cannot stress enough how much food these corals consume. In the past we struggled keeping Tubastraea long term despite feeding the systems twice per day. We achieved success finally by making a frozen food preparation and setting it right next to the aquarium with the sun corals. Every time anyone walked by the tank, they were free to feed the corals with a turkey baster. On any given day they would receive between a dozen to two dozen small feedings.
This is not practical for most hobbyists, however it is perfect for those that work from home OR in an office where they see the tank all day long.
Another option to feeding could be automatically dosing vitamins and amino acids. I dose amino acids as Vibrant which is both a bacterial additive as well as amino acid mix to my aquariums, but I never really considered those as food sources to LPS like sun corals. One company I spoke with claimed that it is possible to provide all of their nutritional requirements this way. I personally haven’t tested this out, but that might be something worth experimenting with if you want Tubastraea but are not around to feed it a dozen times a day. Just set up a dosing pump system and have it done automatically while you are at work or sleeping or both!
Sun corals are very active at night and tend to be closed during the day. Clearly this is not conducive to regular feeding unless you are a serious night owl. They CAN however be trained to open up during the day by feeding at specific times consistently. It does take a while for them to reset their internal clocks so we advise putting in a little bit of food every evening after the lights go out just to make sure they are getting some food on their own terms.
Once they are used to daytime feedings it is easy to stuff them with food every few hours. The only thing at this point that makes feeding difficult is the fish in the tank also figure out that the food shows up around these corals and over time learn to steal food from the corals.
After all this talk about feeding tons of food for these corals, we have to address the elephant in the room. How do you feed all this without absolutely crashing your system. Intense feeding like this could overpower a regular filtration system and lead to sustained high levels of phosphate and nitrate as those uneaten foods break down. Having some phosphate and nitrate in the water is beneficial but overfeeding can cause these parameters to rise to dangerous levels that can quickly spiral out of control and lead to a full on tank crash.
Water Cleanliness
If you are going to try these corals, it is best to prepare well in advance to manage the nutrient load. Here are a few tips I can share.
The first tip is to oversize nutrient removal, which breaks down to water changes and protein skimming, but I’ll also touch on algae filtration and other kinds of filters. I recommend going with a skimmer that has a much higher rating than your current water volume. While I think that skimmer ratings are largely made up figures with no consistency between brands, at a certain point you know when you are getting into monster skimmers. If I get the feeling like I might be overdoing it… that’s likely the sizing I am looking for.
The size of the skimmer is not the only important factor. Skimmer performance is affected greatly by how clean it is. There is a big difference between a skimmer that is regularly serviced vs one that is all gunk’d up. The obvious way to keep a skimmer clean is to employ some elbow grease and scrub it out a few times a week. If that maintenance schedule is a little high maintenance for your lifestyle there are ways to automate skimmer cleaning with varying degrees of effectiveness. For example, giant RK2 skimmers have spray-down systems to clean both the neck and the collection cup. Rossmont skimmers have a controller that allows for periodic over skimming to dislodge accumulated organics. Reef Octopus skimmers have an optional wiper assembly that periodically cleans the neck. None of these automatic skimmer cleaning techniques is a replacement for a full breakdown of the device and thorough cleaning, but they can prolong the service interval and keep the skimmer running better in the mean time.
As for water changes, I am the biggest advocate for doing them. For a heavy nutrient system like this, I would strongly consider an aggressive water change schedule to prevent escalation of phosphates and nitrates. Like with skimmer maintenance, water changes can also be automated using dosing pumps to remove and replenish tank water over the course of the day.
Regardless of whether you go with regular manual water changes or automated water changes, I think it is a really good idea to invest up front into a water holding station if you have the room for it. Having RO water and pre-mixed salt water on hand is a HUGE luxury and makes doing water changes very easy. My fear is if the maintenance is not easy to do, it won’t be done as regularly as it needs.
You may be wondering why I am not recommending algae filter methods. It’s not because I don’t like algae scrubbers. In fact, I was a very early adopter of Algal Turf Scrubbers. I have a copy of Walter Adey and Karen Loveland’s Dynamic Aquaria and even purchased an early model of an Inland Aquatics Algal Turf scrubber. If you have no idea what I am talking about, this is some early 90’s stuff so yeah, we are talking nearly 30 years ago I was experimenting with this stuff… BUT the reason I am not an advocate for it in this application is I REALLY like using Vibrant on a continual high dose to knock down algae growth and to provide a constant source of bacteria and amino acids.
One of the issues that people often run into with sun corals is that they can get nuisance algae around the skeleton whether it be Valona or hair algae. Once that sets in, the corals tend to open up less and it is a downward spiral after that. Less extension equals less food, which leads to more recession, which leads to more algae, etc. etc. So, right off the bat I want to use some manner of bacterial algae control which I don’t think is compatible with algae turf scrubbers. If I’m wrong about that let me know in the comments below, but in our experience with dosing Vibrant heavily just crushes all kinds of algae.
Aside from removing waste directly, you might want to look into biological media plates that are effective in processing nitrogen to less and less toxic compounds. The idea behind these media plates is they provide enormous amounts of surface area for nitrifying and denitrifying bacteria to colonize similar to what happens in live rock. The outer surface of the rock exposed to oxygen grows aerobic nitrifying bacteria which converts toxic ammonia and nitrite into less toxic nitrate. In the core of the rock with little to no oxygen present, anaerobic denitrifying bacteria is present to convert nitrate into nitrogen gas which bubbles out of the tank.
There are subtle differences in the brands that make these biological media plates, and your mileage may vary. In our systems we are trying out a few different ones and see how they do. If they are not keeping up with nutrient levels you can always add more or if you find that the levels are too low, you can always remove one or two.
Lastly, a quick thought on filter socks for mechanical filtration. I don’t love them for this application, but they will certainly work. My concern is there will almost always be food chunks in the water if you are feeding heavily and these socks clog fast. If you are the type of hobbyist that can micromanage their tank, go for it but I like just about all the other methods we talked about more.
Water Chemistry
If things are going well, Tubastraea will start sprouting additional polyps from their base. They actually grow pretty fast for a large polyp stony coral on pace with Micromussa and Blastomussa. As such, they will need a steady supply of calcium and alkalinity in the water to build their skeleton. Calcium is one of the major ions in saltwater. In the ocean, its level hovers around 425 parts per million (ppm). As a coral grows calcium is absorbed from the water and used to forms its calcium carbonate skeleton.
Alkalinity on the other hand is not a particular ion, but rather a general figure of carbonate availability in the water. There are dozens of compounds constantly interacting that make up the alkalinity I salt water. The formal definition of alkalinity is the amount of acid required to lower the pH of saltwater to the point bicarbonate turns into carbonic acid. If you have more alkalinity, it can soak up more acid. Less alkalinity and you have less buffering capacity making the tank more susceptible to chemical changes.
In the wild, the alkalinity of the water is around 8-9 dkh though some aquarists like to overload this parameter a little and keep their tanks around 10 or 11 dkh. There is some belief that having elevated calcium and alkalinity in the water contributes to faster stony coral growth.
One quick note about adjusting calcium and alkalinity: it can be a little tricky because of how they interact. For example, if your reef tank had a calcium level of 300ppm when you desire a value closer to 400ppm, you could theoretically add a calcium supplement to boost it. Unfortunately, reef aquarium chemistry is dynamic and solutions to chemistry issues are rarely that straightforward in practice. Addition of a calcium supplement in this manner often comes with a corresponding fall in alkalinity levels.
This see saw effect between calcium and alkalinity stems from how the two ions interact with one another. The two ions combine to form calcium carbonate and fall out of solution, thus lowering both levels.
If you are experiencing this in your systems, the possible culprit with calcium and alkalinity instability is Magnesium. It may seem counterintuitive that the solution to calcium and alkalinity imbalances is to elevate magnesium, but the three ions interact regularly.
So why Magnesium? Magnesium behaves chemically similar to calcium. It can bind up carbonate ions thus increasing the overall bioavailability of alkalinity compounds in the water. If you are tweaking calcium and alkalinity and getting strange results, you may want to make sure it is not your magnesium level that is low. In the ocean, Magnesium sits at about 1350 ppm.
That should give you a little bit of background on the chemical parameters to keep an eye on. Regular water changes should be sufficient to keep up with the chemistry demands of the corals, especially if you are doing water changes on a more aggressive schedule to help control nutrients like we talked about earlier. Still, it is possible for heavily stocked mixed reefs with a lot of stony coral biomass to need additional supplementation such as kalkwasser, calcium reactors, or two part dosing.
Another thing to consider is how much calcium and carbonate the coral is getting from the feeding. Here at Tidal Gardens, we are basically shoveling shrimp and plankton into their mouths, so all those stony skeleton building ions are in there somewhere. I don’t have any data on that, but they might be getting everything they need from feeding. Just to be safe, it is best to keep the tank chemistry as stable as possible in the range of natural sea water.
Summary
That does it for this coral spotlight on Tubastraea. So what kind of tank do I recommend this coral for? Honestly, I don’t recommend this coral unless the reef keeper is really committed to one of the most high maintenance corals on the market. It needs a lot of food and that can be very taxing on the hobbyists attention as well as the filtration and nutrient management systems of your reef.
Hopefully you found this article helpful. Until next time, happy reefing!
