BIODIVERSITY
Fish are weird. But kind of endearing.
He might look terrified, but the lawnmower blenny’s face is just like that. Huge eyes for excellent vision (they can rotate independently), and a big mouth full of comb-like teeth to scrape detritus off rocks and sand. Is it a handsome look? Perhaps not. But it’s a look. Australian marine aquarium enthusiasts call
Salarias fasciatus the “lawnmower blenny” because, as it scrapes tank rocks, it also removes unwanted algae and helps keep the aquarium looking clean and healthy. But despite the name, it’s not a herbivore: S. fasciatus will take almost any kind of food, even live brine shrimp and bloodworms. In the wild, it mostly seeks detritus, bits and pieces of cast off whatever. Algae? Poop? It’s all good - after all, on the reef, every bit of food gets eaten 14 times.
Outside aquariums, this species is also known as the jewelled blenny and the banded blenny. Why the surfeit of common names? Because like a surprising number of reef fish, S. fasciatus can change colour, from a sort of drab mottled brown that’s hard to see on shadowed rock, to a distinctive black-andwhite banded look - best for confusing predators at dusk by obscuring the fish’s outline.
And when it’s out on the sand flats or feeling sexy, it lives up to the ‘jewelled’ nickname: brilliant silvery dots appear along its flank, while its scale-less skin goes almost transparent-white. Like most fish which perch on rocks, S.
fasciatus has no swim-bladder so can only “hover” in open water. If it stops moving, it sinks gently to the bottom. A helpful adaptation: its pelvic fins are small and stalk-like, and sit in front of its enlarged pectoral fins. This lets it keep its (usually distended with food) stomach up off the ground.
Keeping a marine aquarium is expensive and reasonably complicated, but the lawnmower blenny makes an excellent an helpful first fish. It’s tough as nails, and doesn’t even need to be fed: after a few days you’ll see the glass of the aquarium dusted with algae, and covered in hundreds of blenny
sized kissy marks.