For todays’ blog post we are going to focus on that most recognisable, decorative symbol of the ocean; the Starfish!
What organism could be more symbolic of the ocean in your saltwater aquarium than the humble Starfish?
Starfish also known, as Sea Stars are a kind of marine invertebrate called Echinoderms and are of the class Asteroidea. They usually have 5 arms radiating out from a central disc. There are over 1600 species and they are found on muddy, rocky or sandy sea bottoms spanning the world.
Starfish can regenerate and turn their insides out!
Starfish have the ability to completely regenerate into a new organism from a small section of tissue, this is a way they increase their population assexually (“comets” are new starfish regenerated from a single arm of the original).
Starfish live oral side down and have the ability to externalise their entire stomachs which secrete enzymes to liquefy flesh so it can be absorbed before the stomach is retracted. Their arms are very strong and can open the most robust of mollusc shells and send the contents of their stomach inside to devour the poor creature in no time at all!
A Starfish as a pet
I think a Starfish in a reef tank is a wonderful and interesting addition and really adds an natural authentic flair to your slice of tropical reef. Many species will be peaceful detritus scavengers in your reef tank making a good addition to your clean up crew of marine invertebrates and keep inaccessible recesses of your reef clean and can also stir up and aerate your sandy substrate. Starfish are most happy if kept at a population density of 1 per 3 metres squared.
Choosing the right Starfish…
You must be careful in your Starfish or Sea Star selection because some species can grow very large and/or are insatiable predators feasting on smaller fish and what ever other invertebrates they can get their 5 hands on. Choose carefully and if you have a reef tank ensure you purchase a reef-safe species.
If you have Boxfish, Parrotfish, Pufferfish or Triggerfish do not get Starfish, as these fish are their natural predators, other than these very few species of fish will attack Starfish. Large Starfish may often consume smaller ones and a few shrimp species such as the Harlequin shrimp will also attempt to dine on Starfish. The rest of your tank should leave them alone as they are well-armoured and docile creatures.
Finding a healthy Starfish
When choosing a Starfish ensure it is active and moving around, you should be able to observe its tube feet to ensure it is healthy (tube feet are retracted in sick Starfish). Its body should be firm and not limp.
A good test for the health of your prospective Starfish is to turn it on its back and see if it can right itself, this will help to assess whether or not the stresses of capture and handling were too much. Missing tentacles are not a problem as they will grow back quickly (although freshly wounded Starfish should be avoided as they may develop infection). Also avoid any Starfish with white or dark patches of tissue; this is not a good sign.
Good Starfish for saltwater aquarium use are:
– Blue “Linckia” Starfish (Linckia laevigata): reef safe, amazing colour (you can also get orange or red ones, but blue is the best), very self-sufficient in larger tanks but not tolerant of water chemistry changes.
– The Sand Sifting Starfish (Astropecten polycanthus) Reef safe, aerates your sand bed but eats all the beneficial creatures that make it “live” sand, very easy to care for, ensure it’s well fed if you still want live sand.
– Chocolate chip Starfish (Protoreastor nodosus): Classic starfish shape and reminds you of cookies, good for fish only tanks and FOWLR’s.
– A Brittlestar (various species): Totally reef safe, are very hard working nocturnal cleaners and are the only Starfish I would recommend for your clean-up crew.
Feeding a Starfish:
A great way to feed a Starfish is to place a meaty morsel underneath it; this way no other organisms will be able to steal it from the slow moving Starfish.
Many Starfish species are also omnivorous scavengers feeding on uneaten food, detritus, bacterial films, tiny invertebrates and algae. They do eat a fair bit for their size and so will do better in systems that are not skimmed and spotlessly clean. The bigger the Starfish the less likely it will be able to get into the rockwork to find food.
Starfish prefer good water quality and care should be taken not to remove them from the water suddenly because if any air bubble gets trapped internally in its vessel system they can die. If you want to take them out of the water first place a few of their legs out then slowly bring the body out after a few seconds, this will give them enough time to close their water valve and so be able to be exposed to the air safely.
Special care must be taken when acclimating a Starfish, it must be done very slowly using the “drip” method. Starfish are very sensitive to changes in pH and salinity.