What are the exact measurements of the 55gal? Violet gobys can grow up to 2ft long in the wild, 14-16inches long is more common in captivity though, a 55gallon tank is acceptable for violet gobys although it is the absolute advised minimum amount of gallons for keeping this sort of fish in, a lot depends on the exact measurements of the tank. A 75gallon tank would be better for a violet goby.
They really do need a soft fine sand substrate, and shouldn't be mixed with boisterous tankmates or other bottom feeders.
I found this info on another site;
" An easy way to provide
Gobioides broussonnetii with a good food source is to place them in a marine setting. The live rock in a marine tank provides an ample supply of micro-crustaceans, such as copepods, which make an ideal food source for them. If there is a large enough supply of micro-crustaceans for
Gobioides broussonnetii to graze on in a marine setting, (which is dependant on the amount of live rock and how mature the tank is) only supplemental feeding may be necessary with foods such as bloodworm, algae wafers, and bits of silversides."
"
Gobioides broussonnetii is often mislabeled as the similar species
Gobioides peruanus. The two species are very similar in appearance but
Gobioides broussonnetii is more elongated and thinner as
Gobioides peruanus is shorter, thicker, and has a more deeply purple-colored body. The care for the two species is pretty much identical except that
Gobioides peruanus will not tolerate marine salinities but will tolerate freshwater.
Gobioides peruanus is predominantly imported into the UK so if you live in the UK, chances are you have
Gobioides peruanus rather than
Gobioides broussonetii and vice versa for the US."
Hope this info helps

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