The Urchin Clingfish
Diademichthys lineatus
Family: Gobiesocidae

Many fish come in to the trade these days that are overlooked, but the clingfish, Diademichthys lineatus has only recently been available in the UK. The clingfish comes from the Gobiescocidae family, and although it has some distinctive characters of other familiar gobies it looks completely distinctive from other gobies and so clingfish are the only fish in this family order.  Like many small gobies this fish has evolved to use its pelvic fins as a suction cup so that it can sit on corals or the aquarium glass without being blown away. 

Of the many species in this family very few, if any ever make it into the trade and so little is known about their husbandry.  Luckily the species that has is perhaps the prettiest of known clingfish.

Diademichthys lineatus can be found from the Western Indian Ocean right the way across Australasia, Southern Japan and as far as Fiji and Tonga and is probably the best known of the clingfish and as such more information is available.  Having said this, details of its spawning or breeding seem to be difficult to find although their associations and habitats are known which one day may lead to their captive breeding success.

The most commonly known attribute to this species is that it is generally considered to associate with long-spine urchins of the genus Diadema.  This is not a symbiotic relationship and is of no real benefit to the urchin as the juvenile and young clingfish will prey on the pedicellariae and sphaeridia of host urchins and use it for evidently very effective protection.  Once older the clingfish will accept a wider variety of foods including parasitic burrowing bivalves, copepods and amphipods as well as other assorted small shrimp and other mobile invertebrates. 

In captivity offering this fish live copepods and amphipods will usually provide a premium diet but often start taking frozen mysids, Cyclops, chopped prawn and other prepared meals.  They can however be very slow and picky feeders so too much flow may simply blow the food away from this inquisitive feeder.

Telling male from female couldn’t be easier with this fish as their sex is determined by the length of their ‘snout’.  Males have a shorter stubby and more rounded snout whilst the females are much longer and thinner. These distinctive pointy mouths sometimes gives them the common name “Long Snout Clingfish” and makes choosing and keeping a pair much easier and although they are not territorial or seemingly aggressive it will always be recommended to keep an even number of males and females.

Tank mates for this fish should be chosen carefully as they are shy fish and boisterous or over-active tank mates may lead to this fish becoming very reclusive so an ideal environment for them would be a well established seahorse / pipefish tank with beds of caulerpa or other macro algae meaning there is plenty of established micro fauna.  There appears to be no aggression from the clingfish towards other small gobies, dragonets or mid water swimmers such as cardinals and small wrasse.

Some of the so-called Urchin Clingfish are found in different situations to those associated with the long-spine urchin.  Some may live on branching small polyped hard corals, feeding largely off parasites that may pray on them.  Other populations are found amongst vast algal beds where the clingfish takes on a more vibrant red colouration rather than the usual darker red/black.  In these situations it is thought that they are able to survive exclusively on the micro fauna living amongst the algae and as such may actually make them more suitable specimens for aquarium success.  Those that are currently coming into the British aquarium trade however appear to be the usual black base colouration.  Occasionally it has been said that they may pick at the mantles of Tridacna although this may well just be a sign of an under-nourished clingfish looking for alternative live foods sources.

Resources:

A Pocket Expert Guide to Reef Aquarium Fishes by Scott W. Michael

Fishbase - http://filaman.ifm-geomar.de/Summary/SpeciesSummary.php?id=12891

WetWebMedia - http://www.wetwebmedia.com/clingfishfaqs.htm

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