It all depends on the alkalinity of your tap water.
If you have a low alkalinity, crushed coral sand will raise the pH a little, and it will help buffer the acidity from fish urine and decomposition by-products, which can by important in a tiny tank like a 10 gal.
The smaller the tank, the easier it is to become acidic have a pH crash.
If your water is soft, with a low alkalinity, crushed coral would help for fish like desert gobies. For Apistos there would be little need for crushed coral because most prefer soft water, and more acidic conditions.
If your tap water has a high alkalinity already, and is hard, then an inert type sand may be adequate, for the gobies or any hard water fish.
Apistos might be out of their element if your water is especially hard.