Funny you say that I just came up with how I can expand "AGAIN" the pond doubling the swim area and water volume while lessoning the energy demand.
Basically i would have to open up the negative edge at the end of dead pool and build out over the cistern. this would give me water depth of about 3 feet maybe 4 but it would require building on top of the cistern. but i could make it about 30 feet long and i'd stick with around 10 to 12 feet wide for ease of cleaning and maintenance. But it would not be straight it would be more just narrow in one spot and opens in another.
This would require building on top of the current cistern . i could remove the blocks making a 12x12 area that would now be able to be 6 or 7 feet deep. but in doing that would expose the bottle dump i found from when they built the house. That was a practice before the 70's to dig a pit in the back yard and dispose of all the paint cans ,lumber, beer and booze bottles, left over tile ect. So I got away with putting the cistern in there once i'll probably leave that sleeping dog lie.
Make an overflow where the water would drop into the cistern thats what i have now it would just be relocated and improved.
Then i could have one heck of a stream / waterfall running back toward the bog ending at the base of the bog. This would then require my pump to simply push a 3" line up 8' and over 20' cutting down about 6 feet of vertical head and 30 feet.
And of course allowing for more fish and it would certainly give the fish a good swim from one end of the pond to the other. the pond is like 26 feet wide across the patio the from the patio to the now negative edge in dead pool is like 32 feet. Then with the addition im thinking another 25 feet for a grand total of 80 + feet one end to the other now that would be cool.