Pool Bog size for Pool Pond?

[PoolPond]

What size pool would I need for a bog next to my pond pool.
My pool pond is 12' diameter, 2,500 gallons, 3' deep with 18" in ground and 18" above.
To have a waterfall I'm looking at 24" high round bog pool on ground so I have 6" drop.

 

[Mmathis]

I seem to recall that the optimal size for a bog is 30% of the volume of the pond.

 

[addy1]

Any bog size is a plus. I have had small ones and now a large one. The large works better, full of plants.

 

[GBBUDD]

MINIMUM OF 15 % 30 OR MORE OPTIMUMLY the main sizing is due to your fish load larger the breed the larger the bog

 

[Bluerooster]

30% of the surface area of the pond, give or take. bigger is better.

 

[PoolPond]

I'm going to make it the same depth as the pool so it doesn't matter if it's volume or area.
This will give me 18" of drop for the water fall.