We’ve recently added a long-bodied fish called a striped anostomus to our aquarium. It seems to be feeding well, but appears to be having difficulty in maintaining its balance. It spends time with its head pointing downwards. Is there anything I can do? Could it be suffering from a dietary deficiency?There’s no need to worry. This is actually quite normal behaviour for these and other anostomus fish, and is actually the reason why they are also sometimes known as headstanders. These fish are mainly vegetarian in their feeding habits, and should be fed on a prepared diet of this type.  Beware, as they can sometimes damage the more delicate plants in an aquarium.