That's great to hear Snow!

Okay so we are looking at a pond to hold around 20 goldfish?
Hmmm I'm not sure on the recommendations for stocking in ponds... tell ya what, I shall go and ask a friend of mine who builds ponds and get back to you Oh also which part of the world were you in again?

With transporting fish, I would imagine buckets filled with water and perhaps an air stone or something? Hopefully one of the others will be along soon, I'm not entirely sure!

As for location, I think an area that gets sun for a portion of the day i.e. the morning or afternoon, as I imagine if it gets sun all day you will have a lot of algae to contend with!

I don't think guppies would be a good mix, the goldfish would more than likely eat them being that much bigger! I would keep it at just the goldfish really

Ponds don't need decorations either, so I would just leave it barebottom and not add anything asides from the plants. If you have weeds, you could always keep some separately in an empty bucket or tank and let it grow, so that you'd always have a supply to replace any eaten plants.

-Edit-
Heard back from my friend this is what they say;

"The rule of thumb is 1 inch of fish to 1 sq ft so if the fish is 3 inch then it needs 3 sq ft, a outdoor tank with good filtration, at a guess not knowing fully how many and of which sort about 4500l but bigger is always better."

Perhaps if you let me know what types of each fish you have i.e. fancy, single tail? I'll ask them, because if they're mostly single tailed they will need a bigger pond again once they've grown, or you'll have to re-home some

Heya, got in touch with my friend and they said this;

"the commons are the main issue here because they can grow to quite a hefty size so the hole would have to be quite large, if they live in southern india they could grow up to two ft, because of the conditions these fish can grow to some very big sizes in warmer climates, we have very cold winters here which slows there growth rate, the other fish would be happy in there but the commons will out grow that tank eventually, and he will have to consider expanding or rehoming the commons, also they could try some fine mesh or net over the pond to protect from snakes. in warm climates two ft is deep enough, and the bigger the surface area the better it will be."

Hope this helps!

As for the two ponds joining hole? Why not just build one massive pond rather than two smaller ones? I'm not sure how different sized ponds will help with snakes? Wouldn't snakes drown in the water anyway or can they swim?