A siphon will work 24/7, no gas, no refilling, cheaper and easier - just a thought.

If you plan on renovating the pond, it would be helpful to temporarily divert runoff so you can work with a dry basin. Although a trackhoe can still dig fine underwater - you won't have access to basin for compacting soils or other work if you wanted to do that. Another concern about not being able to see the basin during renovation is running the risk of hitting a gravel vein. Underwater you'll never know it - but dry you will and can fix it when you encounter it.

I would definitely check google earth and verify there are not BOWs upstream of you that could flood during heavy rain events. Reintroduction of invasive species would be a nightmare, obviously, and your efforts and money would be wasted.

Many men go fishing all of their lives without knowing that it is not fish they are after. ~ Henry David Thoreau

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