You are probably fine as is. You certainly don't need winter protection in Ca. I am now in North Carolina 7b and my goldfish can tolerate a completely frozen over pond. Of course, my pond is 2.5' in the ground while yours is probably exposed on the sides. But still, yours is in zone 9 not zone 7. I also have a water catch pond from a french drain that I use for irregation. It has no pump or anything, but fish still do well in it as well.

It would probably be good to have some flow and perhaps a little fountain or something, but it is not necessary. A small pump is cheap. If water spilled from a little pondette on the side or something, you would probably find that pond roots in that edge container (or adjacent in the regular pond) would catch crud and act like a filter. Your fish load is probably correct now. You will probably find that future eggs will mostly be eaten.

Thanks for the reply, I was wondering what the fish load would be limited by first - toxic water or depredation of eggs and fry. When the plants stop growing it seems like the water will go bad pretty quickly.

I use a old pool float to shade my pond half of the year. It isn't in the water just across the top. It also protects against green herons. The old rule was an inch of fish per gallon but you can push that with filtration. Gold fish and comets can be messy fish. Koi need much, much more real estate but you don't have any of those.

That you don't feed is really helping keep things from rapidly declining. During the summer, sometimes water doesn't hold enough oxygen. You have probably gone by small lakes and can see the algae that looks like bread soaked in water all over the top of the lake. Many lakes get an algae bloom that sucks all the remaining oxygen out of the water leaving the fish gasping at the top and then dead in the morning.

You could add a good size airstone and airpump for the summer . I keep 4 stones and 2 pumps going all the time. I also have 2 filters, one bio and one pressurized. At one time I had too many fish for the gallons of pond. Now that things have thinned out due to age, things are much more stable.

By providing some shade your water may clear a bit. Algae is a natural thing in water settings and your fish are eating it. Some algae is a good thing. If you run your net through it and its full, well, that be a bit much. I would pull as much out as I could and compost it for the garden. There are chemicals that will get rid of algae but... I have used them sparingly in the past and only at half dose. This year I just had a couple of weeks of a tiny bit of string algae. I gathered it and fed it to the fish, It was in my waterfall area so they couldn't get to it.

Algae also feeds off fish waste. You have a plant and that helps balance things. Plants and fish make a happy pond. You could add some oxygenators like hornwort or parrot feather aquatic plants ( many more I can remember).

Each state has some restrictions on water plants. I can't have water lettuce here because it's invasive but it can really clean up a pond. Same with Hyacinths. I used to keep a stock pond of those in case my pond needed some help but the Koi love to eat them and that makes a mess.

You don't have to have crystal clear water. There is an upper limit on fish load.

You can do water changes weekly, say 20%. If you are refilling with city water, then you might have to detoxify the chlorine. For that I use "Prime" by seachem.

You can and should have a variety of plants. Marginals will go all year. Don't plant using garden soil. Use small rocks and gravel. Lillies have dormant times. You need to feed your lillies when they start to get active next spring. Use an aquatic pellet fertilizer. YOu place it in the pot under the rocks near the roots. You could also have a pot of water iris which are good for water purification. Yellow Flag does a good job. I had to order it on line. I also have Game cock which is proliferous so much I had to cut it up and throw away 1/2.

You might find a garden center with pond plants.

Watch for spawning behavior and maybe water changes would eliminate some eggs??? don't know, I have all males. I didn't plan it that way.

Don't do multiple changes of whatever you have been doing. If something is helping you won't know what exactly it was. Likewise if it causes a problem. Do small changes and maybe keep a journal so you know what works for your unique pond environment.

Good Luck!

Thanks for the advice. I think I'll add a small fountain pump in a bucket of filter material.

For a long time I never saw any goldfish - only the lack of mosquito larvae was a clue that they were there. My lilies are potted in normal garden soil covered with an inch of gravel. The pots are on bricks and that creates a safe place for the fish to hide. I fertilized them last year, but haven't bothered this summer.

The water is green, but no algae build-up. I have never done a water change or used chlorine removal chemicals since the initial fill. Water is expensive these days.

I have meant to get some Elodea from the fish store, it should overwinter ? as I have seen it in very cold waters like the Truckee river.

The Elodea should be fine. There are several aquarium plants that do well outside in 9B CA. Bacopa and Ludwigia are two commonly encountered plants.