Were I to mention bottom feeding fishes to the average freshwater aquarist, I'm sure he or she would reflexively think first of the catfishes, and then the loaches. Yet there are other potential occupants for the substrates of our tanks, and there has been increasing interest in freshwater gobies as ornamental species for tropical to room temperature aquaria. In past decades gobies were associated more exclusively with marine and brackish aquariums, so it has taken a while for interest in freshwater goby species to catch up. Chief among the freshwater gobies to stimulate attention of late, has been the grazing genus Stiphodon. Among the great clade of gobies, members of this genus are considered to be herbivorous, stream living specialists, that adhere to boulders and cobbles whilst feeding on the biofilms that naturally occur on their surfaces. For this niche their guts are elongated as in most herbivorous vertebrates; their mouths are underslung as is common in benthic fishes; and their teeth are well suited for use during scraping. Stiphodon is a taxonomically confusing and unstable genus that confounds professional ichthyologists, who had formerly regarded all members of the genus as members of only one, variable species, S. elegans. Where the identity of a Stiphodon population or morph with S. elegans is uncertain, they are best referred to as Stiphodon cf. elegans, do as to express both skepticism and the impression of similarity.
One of the more distinctive species of Stiphodon in the hobby, is the cobalt blue or opal cling goby, S. semoni. In the freshwater tropical trade, this species can also be known as the neon goby, but it must not be confused with the Atlantic goby species of that name, which is well loved by 'reefers'. The cobalt blue goby is quite a small aquarium fish and it grows to only 5 centimeters long, or 2 inches. Despite its distinctiveness, it is still sometimes mistreated as S. elegans, which is actually of the same approximate length. (Online I have seen the name of S. elegans most commonly associated with a 'green riffle goby'; but as a non-specialist, I can only express doubt that such identifications are accurate. If ichthyologists cannot sort Stiphodon systematics, then aquarium retailers may hardly be expected to do better!)
The natural range of S. semoni is throughout the Indo-Malayan archipelago, and onto the Solomon archipelago and Queensland. Such a broad distribution is possible because stiphodonts are not freshwater fishes throughout their whole life cycle: they initially drift out to sea, and there join the zooplankton as larvae, before returning to freshwaters when they enter their juvenile stage. Supposed S. semoni from the Philippines and perhaps other more northern localities, are nowadays regarded as a distinct species, named S. atropurpureus, also called a cobalt blue goby and also growing to the same adult length as S. semoni. Both these species appear to be found in the aquarium trade.
Online resources aimed at aquarists tend to be strangely vague, when they are specifying how to care for stiphodont gobies. However the ecological data I am aware of, reveals both S. semoni and a sympatric S. cf. elegans to inhabit streams with a temperature of 23 to 25 degrees centigrade, and a pH slightly above 7, yet below 7.5. Although websites say that these gobies live in water as warm as 28 degrees, I haven't seen any data that corroborates this, which is maybe because running water has a cooling effect. Where stiphodonts compete with other fishes they tend to be one associated with the upper reaches of streams; otherwise they are more broadly found throughout their entire streams, including the more sheltered pools that form. It might thus be seen that they are not strict microhabitats specialists as some sources claim, although they are associated with good quality, flowing freshwaters. As these are specialized fishes that graze biofilms upon rock, they should be kept in well illuminated tanks that have an aqua scope of cobbles and larger rockwork: the bright light will encourage the algal biofilms on which these gobies subsist. These are essential for these fishes to survive in the wild, although their natural habitats also feature sand. Their aquarium water must be clear, well oxygenated, and generally of a high quality; the water movement should be greater than that which is usually in a tropical community tank, yet it need not be forceful.
Stiphodon sp. should be cohabited in small numbers, and they are universally peaceful towards other small, ornamental fishes and shrimp, that share the same requirements. They are also not damaging to plants, though most of our aquarium plants do not prefer the stream environments with which Stiphodon are best associated. Because these gobies feed on periphyton, they should only be accommodated in aquariums that are already rich in algae. But they do show interest in such suitable foods as algae wafers, and it is reported, even slices of cucumber. Despite their extremely strong herbivorous leanings, Stiphodon may show interest in meaty items, but it must be stressed that these are basically vegetarian fish, and they must have access to an essentially vegetarian diet, not one based on animal protein.
