Growing Soft Corals in a Saltwater Aquarium
Adding coral is an exciting next step so I’ve tried to answer as many questions as possible on growing soft corals in a saltwater aquarium.
You can use the links below to jump to the section you’re most interested in or better yet, have a read through all of them!
Quick Links:
- What is a soft coral?
- Types of coral
- Most popular soft coral types
- Do I need to feed soft coral?
- How fast do soft corals grow?
- How many species of soft coral are there?
- What do soft corals need to grow?
- Are soft coral easy to keep?
- Do corals need white light?
- How much light do soft corals need?
- Conclusion
What is a soft coral?
Soft corals (Alcyonacea) are in fact a type of invertebrates, which belong to the much wider invertebrate umbrella shared by shrimps, snails, starfish etc. They generally look more soft and fleshy in comparison to hard corals.
Most soft coral have tiny organisms called zooxanthellae that provide the coral with energy. They are also responsible for giving them their vibrant colours. However, zooxanthellae are not always present in soft coral.
They are called ‘soft’ because they do not have hard stoney skeletons (like LPS and SPS). These stoney skeletons are made up of calcium carbonate and need a constant supply of calcium in order to grow. This is the reason soft coral are easier to start with for beginners to saltwater tanks. They don’t need as much calcium or stronger lighting that hard corals do.
Types of coral
There are basically 3 types of coral:
- SPS - Small Polyp Stoney Coral (hard coral)
- LPS - Large Polyp Stoney Coral (which has a stoney base)
- Soft Coral
Most Popular Soft Coral Types
There are so many different types of soft coral you can add to your saltwater aquarium. Below I’ve listed some of the most popular types.
You can try your local fish shop (lfs), an online seller or local Facebook group to source new coral.
For a more comprehensive list see my article on soft corals suitable for beginners.
- Zoa (Zoanthus)
- Leather (Sarcophyton)
- Clove Polyps (Anthelia)
- Ricordea (Ricordea)
- Green Star Polyp (Pachiclavularia)*
- Pulsing Xenia (Xenia) *
*Be careful with both these corals as they grow a little too well and can end up taking over your tank, especially the Xenia.
Do I need to feed soft corals?
As long as you have fish in your tank, you don’t need to feed soft coral. Particles of food and fish poo will drift their way in the currents in your tank.
Typically soft coral need gentle flow due to their gelatinous structure, and in such a flow they are able to snag food passing by. This is usually provided by a wavemaker or powerhead.
How fast do soft corals grow?
Soft corals are certainly quicker growers in the right conditions than LPS and hard corals. They do not need to lay down calcareous stoney feet therefore the majority of their energy goes into branching outwards and upwards.
Soft coral stretch themselves outwards, sometimes causing the new growth to sever from the mother colony. The disconnected growth quickly becomes a new animal and so they spread.
Some soft corals such as Pulsing Xenia can grow as much as 1 inch per month however for the majority of soft coral, it is less than that.
How many species of soft coral are there?
There are more than forty species of soft coral divided into five sub groups. Not all of these however, are available to the hobbyist.
What do soft corals need to grow?
By maintaining the parameters below you will be creating the ideal habitat for soft coral.
- Calcium - 380 - 430ppm
- Alkalinity 7-11 dkh
- Magnesium 1350 - 1410ppm
- Salinity - 35ppt
- pH - 8.2 - 8.4
The above parameters are measured with marine specific test kits, apart from salinity which is measured with the use of a refractometer.
To provide soft coral with gentle water movement, you should add a wavemaker or powerhead. This should not be directed at the coral but emulate the multi-directional flows of the sea. In their natural environment, currents bring oxygen and food particles to the coral.
Are soft corals easy to keep?
Growing soft corals in a saltwater aquarium is definitely simpler than growing hard corals. Soft corals are a lot less fussy which makes them low maintenance and perfect for beginners to saltwater tanks.
The reason they are called ‘soft’ corals is that they do not have a stoney skeleton like hard corals do. The fact that hard corals have an stoney skeleton means that they are voracious calcium consumers. That, along with stronger lighting, is what makes them trickier to keep than soft corals.
Soft corals should be placed far enough from each other, allowing them room to grow. Soft corals don’t sting as LPS do, but they do excrete a type of poison to prevent other corals from getting too close. This poison does not affect people, but is more of a warning to other corals.
The exception to the poison rule is that excreted from Palythoa coral. This soft coral kept by many enthusiasts needs to be treated with respect. While in the water they are safe, but when removed from water they are capable of releasing Palytoxin.
Incidents of Palytoxin poisoning have been in the news over the years when uninformed aquarists decide to clean their rocks, or cut or boil them (never boil live rock!). This toxin is capable of killing an entire family living in a house if Palytoxin is released into the air.
Do corals need white light?
Yes, corals need both blue and white light to grow well, and this includes soft corals.
Most corals are fed by microscopic algae called zooxanthellae which have a symbiotic relationship with it’s host coral. They are what give the coral their energy to grow and reproduce. The zooxanthellae, much like plants and trees, create energy via photosynthesis. If you remember back to your school Biology classes, photosynthesis helps plants convert the light of the sun into energy.
Now, not all soft coral have this symbiotic relationship and therefore rely more on water conditions to absorb the required nutrients. These are non-photosynthetic, like sun coral, and therefore do not need light at all. These are not as easy to look after and are therefore best left for experienced aquarists.
How much light do soft corals need to grow?
Soft coral need very basic lighting. When you start adding hard corals, SPS and LPS, that is the point at which you need to stronger lighting. Unfortunately it is more expensive but an investment which I think is totally worth making.
You need blue lighting on for around 8 – 12 hours and white lighting for roughly 6 – 10 hours per day.
So there you have it!
You should hopefully now know that growing soft coral in a saltwater aquarium is the perfect place to start when moving on from fish.
There are many benefits to adding soft coral to your reef tank. They’re less fussy, don’t need expensive lighting and grow quicker making your tank look more mature in much less time than it would with hard coral.
Before you know it though, you’ll find yourself eyeing out the hard coral!
ref 1 https://als.lbl.gov/coral-exoskeleton-growth-begins-inside-living-tissue/
ref 2 http://www.wetwebmedia.com/soft.htm
ref 3 https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/palytoxin
ref 4 https://www.independent.co.uk/news/uk/fish-tank-poison-toxin-coral-palytoxin-newport-a9047251.html