Mushroom Corals, Actinodiscus Types
©, 1997, Albert Thiel, Update 3
Actinodiscus corals or mushroom corals have been around for as long as hobbyists have been keeping reef tanks. They are probably one of the easiest soft corals to find although getting a nice assortment is not the case. Purple and reddish ones are widely available. Other types are not.
Mushroom corals are soft corals and have no exoskeleton but grow on rock. The rock does not need to be flat, it can be shaped in just about any form.
The name mushroom is derived directly from their appearance: a short to medium length stem, surmounted by a cap. The cap can be real round or somewhat ruffled depending on the type. Generally the stem is short and not all that visible.
The corals can be mono colored or multicolored, can be smooth or rough, with knobs or stripes running across the cap from the inside towards the exterior.
Mushroom corals are generally considered hardy but that does not mean that they take abuse real well. What is meant is that they can do well in water quality of various parameters. They do not do well when sudden changes to that water quality are brought about though. The latter is perhaps one of the most commonly made mistakes. Mind you, sudden changes affect everything in the tank, including fish. Sudden change brings about stress, and stress often leads to disease and the appearance of parasites.
The changes to really avoid are the temperature, pH and salinity ones as they are the ones that will cause the most stress. Mushroom corals will appear to shrivel up and become real small when overly stressed. Certain kinds do not take lots of stress and shrivel up faster than other types. More on this later.
Mushroom corals not only appear in many forms but also vary greatly in color. Most of this has to do with the environment they came from and what kind of lighting they were receiving there. This in turn influences their pigmentation and determines what colors are predominant. Some are just one color and others have multiple colors. It should be noted that very few Mushroom corals have actually been named and that you will see photos of them just mentioning them as Actinodiscus species. Kind of makes you wonder why they have not been identified since they are plentiful.
In addition to the differences in shape and color you will come across differences in the texture of the polyp, going from real smooth to knobby and even in some cases with tiny tentacles. The variety is endless. You may have seen this yourself going through magazines and books. This great variety of types is what makes these corals so interesting and makes them add color and appeal to your aquarium. Note that these corals are found in all oceans where reefs are present. Even the State of Florida has their own varieties.
In nature around natural reefs, Mushroom corals are found in clusters, sometimes so dense that individual specimens overlap. This same arrangement can easily obtained in a well kept aquarium as Actinodiscus reproduce fairly easily and in may different ways (budding being probably the most common one).
All that is needed to achieve this is to make sure that the water quality parameters meet the standards outlined in this article and that no predation occurs. It is uncommon to find individual specimens that are not part of a colony, although some Authors have reported seeing this happening, speculating that one or several specimens detach themselves and resettle not too far from an existing colony, to start a new one. This will happen in the aquarium from time to time as well.
This poses a challenge for the hobbyist, as loose Mushroom corals die if they are not somehow tied down so they can reattach to another piece of rock.They are perhaps one of the hardiest corals around although not all hobbyists seem to accept this fact because they may have had problems in keeping them alive. The reasons for this can be varied and have more often than not to do with water quality and lighting, more so than with disease or predation. Indeed not all of the Actinodiscus species fall into the same requirement category. Hobbyists need to experiment to some extent to determine what the best lighting conditions and what the better current strength is for the types they have acquired.
Most Mushroom corals will do fine in medium to stronger lighting. Ideally though, they should be observed for their reaction to different intensities and the positioning of the coral may then need to be changed so they open more fully, once the right lighting amount has been determined. The same applies by the way to the amount of current they should receive. Some varieties like strong current and others will do better in moderate current conditions. There is no way to predict this or make recommendations that apply across the board. Testing with various current strengths has been undertaken until the right amount is found.
Observing how various specimens react to differing conditions is best done by subjecting them to particular parameters for one to two weeks and taking photos at different intervals. This gives the hobbyist a good basis for comparison and something tangible to base decisions on that need to be made in respect to lighting and current. Trying to remember what or how a particular coral looked two weeks ago is just about impossible. Looking at photos though will give you an immediate feedback and will allow you to decide on what is best and what kind of current and what kind of lighting produce the best conditions for your Mushroom corals (and others as well).
I stated earlier that these corals are hardy. They are. It is not uncommon for a tank be in real bad condition and for a hobbyist to loose many corals while, surprisingly enough, Mushroom corals that appear to have died and have shriveled up completely will recuperate once conditions in the tank have been reestablished to acceptable levels. I have seen this happen over and over again. This leads me to suggest that you should never dispose of a Mushroom coral because it appears to be in bad condition or shape. Adjust the current, lighting and what ever else needs to be changed and you will probably find that your Mushroom corals will reopen as if nothing had happened.
It is important to realize that feeding and thus growth, is determined not only by lighting but also by what nutrients these corals can uptake from the water. Using a truly complete additive becomes a necessity if you wish to maximize the feeding of Mushrooms in your tank. It is not sufficient to use just any additive. Use one that contains a great number of elements. Newer ones on the market may very well have over 200 components, those are the ones to use.
Recommended water quality parameters:
pH: 8.2 to 8.4
s.g.: 1.023 to 1.025
Temp.: 77 to 79 degrees F.
Calcium: of no concern but if you have stony corals the level should be around 450 ppm
Nitrates: below 10 ppm
, total nitrate
Phosphates: below 0.04 ppm
Silicates: below 0.5 ppm
Dissolved oxygen: 7 or higher
Do not use mechanical filtration
Use a really complete additive
Add iodine to your tank daily. Follow the manufacturers recommendations
Current inside the tank (laminar): moderate to high but not directed at the Mushrooms.
Keep bristleworms out of your tank
Keep an eye on Hermit crabs. They should not be crawling over your mushrooms
No algae should grow on or in between the individual polyps of a colony. If this is the case you either have too high levels of phosphate or silicate or both.
I hope this helps some. Albert has never steered me wrong yet!
As he mentioned, rapid changes, of any kind, are a real problem many just ignore. Those temperature swings are deadly if they occur too fast. Same with salinity and Ph to a lesser extent.