First, thanks for the advice on the water hycinth, such a beautiful plant. I am definitely going to look into that.
The pond is actually 17in deep. It is pretty deep for the gallons so it is deep compared to it's surface area. We than added an extra 10 gallons from ridged stream/waterfall liners. It's not much but it did increase the surface area quite a bit and will aerate the water. I made a very simple filter as well, using an Eheim filter pad which I covered with rocks at the top.
Right now, i am running a little fountain pump we had laying around. It is probably only about 50 gallons an hour max. Our plan is to buy a solar powered pump that is 210 GPH (or around that 200+ GPH). It works night and day due to a battery. I am not sure how much the GPH fluctuates over night or in different lighting conditions. My mom has been using smaller ones that are 5+ years old that are still dead reliable. I can only imagine newer, more expensive ones are better, or at least the same, so I am confident it should work. Does the GPH sound about right? From my research it does, the added strem/small waterfalls are only about an extra 8-10 in higher than the top of the pond.
As for fish, I bought 4 feeder goldfish to get some beneficial bacteria going. I had already figured that they would die and then when I went to buy some, the person at Petco said that they would not survive and were extra bad compared to what they normally would have. We all know they arn't the best for fish, especially feeder fish so you all know how that goes. I figured no big deal, that will get some ammonia going. Well, I drip acclimated them like I would for any other fish and they all survived and look super healthy. This may be a problem down in a while but for the next few years, I think it will be fine. If they all life and grow too big, I can easily get rid of them as a few private and public ponds take in overgrown cold water fish.
And for the weather. I am in the CA Bay Area (East Bay). I would say water in a container only freezes ever 3-4 winters. That would be about a few mm, never anything bad. Occasionally we will get a freak winter where it will freeze harder, maybe once every 15 years. Last winter it snowed in my area, something that never happens here. The summer is hot, 80-90 degrees consistently, but probably highs of about 75-85 for most of the summer. The early spring and late fall are in the 50-60 degree range. So, it's pretty optimal weather from my understanding compared to most other places in the US. I am not concerned to much about the weather.
Basically at this point, my main question is the pump. Is 200ish GPH about right? Most people say it is fine, some say it is too big, a few people say to go bigger. I don't think we are going with a filter at this point, other than my makeshift setup. Although my mother already ordered the pump, it is on back order until late July so we can change our minds. It doesn't have to be solar either, my dad can run power out there no problem as good or better than a hired electrician so that can be done safely. We may go that route as the solar pannels are bigger than what my mom wants, plus we can add other things if wanted/necessary. We do have 6 GFI outdoor outlets within 15 feet of the pond for temporary things.
Thanks for the help so far. Again, this is my mothers pond, I am just doing all the work for her. She is very handy and could have done it all herself, then framed a house around it if she wanted lol, but as handy as she is, she doesn't like constant projects. She will maintain it as she has to but doesn't want to add any work if it won't drastically make things better.