Remember also that koi and goldfish do cross breed. I don't have koi, I think I recall people saying the babies are sterile.
I'm no expert but theres many here with more years of experience then I. But more then happy to help. I wish i had made a list and put it up to the forum and get the input from others here. Like Jhn with making pockets in the dirt before laying downhearted liner to control roots. or lisa with a negative edge instead of a skimmer theres a lot to consider that will be written in stone sorta speak once you start the liner.
Ditto what Addy said. Minnows will multiply quickly, as well. If you are going to start with a few just to control mosquitoes, I would say go with some pretty goldfish (Shubunkins). Don’t be in a big hurry, as you’re going to be busy getting your water parameters adjusted in the beginning so you only want a few fish when you start out.
I was having issues with the sides from lots of rain. Its not unheard of for us to get 8-10" of rain in 24 hours. I was planning on using basketball size rocks for the walls. Bad idea?
I'm not in a hurry for fish. Just want some smaller mosquito eaters from the start.
For a 6 foot tall wall stacked with basketball sized rocks id be very concerned about if someone is swimming in the pond. or just doing maintenance that the stack is way to unstable as a Vertical wall the walls should be pitched but even then there own weight can put enough pressure to pick up/ push out a weak link lower in the pile and start a house of cards. It should be mortar. Or like the aquascape builds for 6 feet they if using smaller rock would do 2 foot tall shelves even at that your looking at 3 rows of twelve inch rocks bottom row partly buried by rocks on the floor then the same row needs to be 4 too 6 inches higher to hold back the rock on the next shelf. and I little angle on the wall would be easier to build. But to me if you have watched my videos underwater large boulders to me look way cool very natural and it can be very stable but keep in mind if a big rock shifts it could be big trouble for a swimmer. Yes its harder to set the big boys but it can go very fast to. Making caves is easy.
I run a 12000 gph pump but I do not send that much to the bog. I have it split 2 ways a 3" pipe runs 40 feet to the Bogs then splits to two 2" lines one to the aquablocks bog and the other to the peastone bog both with ball valves to control the flow rate. then a 2" line that goes into the pond as two return jets creating circulation. I believe I have a little to much back pressure I may be choking the pump a little but it does not whine in anyway. With your pond I would look hard at circulating pumps to the pond alone its good size they do have power heads similar to an aquranium.
I was planning on trying to get the liner in today but after think about this I have decided to wait. I was a bit concerned about this with our earthquakes but I think I need to redo the one tallest wall. It’s a 90 degree wall. I was just going to use pond foam to tie all the rock together but I think I will cut another shelf in at 3-4’ high and get rid of that huge wall. Thanks for the advice.
I’m leaning going that route as well. Hoping to speak with a salesman today that is knowledgeable and can confirm this would be the correct size for me. Thanks