We usually recommend 20g for the first
goldfish and 10g for each additional goldfish because they produce so much waste. That said-
Because of the body shape of a Moor they don't compete for food with faster fish very well. Most of the minnow family can handle the cooler water goldfish need but they are too fast and the Moor would never get to eat.
Dojo Loaches appreciate cooler water and would be a bottom feeding fish so no competition for food. The water would have to be kept especially clean because Loaches are sensitive to water quality.
Carol