10 gallon?

[QuickQuestion]

Hello! I have an empty ten gallon tank that previously held fish and at one point, hermit crabs. I've seen things say a pair of gerbils can live happily in a ten gallon but then I've seen other things say that a 40 gallon is much more ideal. Of course I only want to consider this as an option if it is ethical. I still have quite a bit of research to do but I just wanted to know if this was an option since I already have the tank. I would of course provide them with lots of enrichment and time out of the cage as well. 

[catnut]

a 10 gallon is too small for two gerbils esp. if they are energetic, at least a 20 or pref. 30 or 40 gallon is much better unless you can get a topper but i prefer one level homes for gerbils.