Most mosquitoes don't like moving water surfaces, but tolerance varies by species and I don't know about yours. (Also, some plants don't like the moving water surface, like water lilies.) So running water streams, pondless waterfalls, etc. might be a possibility. A lot of marginals can live in boggy soil (no standing water) if you want to set that up with a liner under the soil, possibly in conjunction with the above.
Fish and BTI (active microbe in mosquito dunks) are really the only control I use here. Some fish can live off of algae, and will just snack on any larvae that show up, so don't require any care. I don't know of any other biological controls that are efficient enough to make sure none of the larvae mature.
Wish I could offer more suggestions. I live next to a river delta here and we're very conscious of mosquito-born diseases in the area, so I know it can be a serious problem. Short of sealing an actual mosquito net over the pond, I don't know how to stop mosquitoes themselves.
