If you don't have lots of algae, I would avoid the algae eaters completely unless your heart is set on a specific type. For the goldfish tank--IMO, not worth the risk. First, very few will tolerate the cooler temps very well, adding an algae eater means increasing the bio-load substantially, and many algae eaters will attack and suck on the goldies if they don't have enough food. In the 10--again, JMO--but manually cleaning the tank to stay on top of the algae is a better option. Many will outgrow the tank, again you're significantly increasing the bio-load, and many of the smaller species that won't outgrow are expensive, sensitive species that can be hard to maintain in smaller setups.