Funny story - when we first set up the sugar kettle, I went to our local pet store and told the "fish guy" that I wanted some fish to put in it. I had picked out a few fish that cost about $30 each. This guy was like, "No, you're just starting out; here's a bag of 12 fish for $4. Let's start with this." I've had them for 8 months and they are awesome! I am really enjoying them. Thank you all for helping me to take care of them!
That's a business you should always go back to. That was excellent advice. That store will probably always do you right. Reading up, it sounds like your son got a hard reality check on what tropical fishkeeping means: tropical fish are aquarium fish, not pond fish. They never really stood a chance in the pond. That same store that gave you that bag of starter pond fish probably would have taken the unwanted tropicals back too and rehomed them if you'd asked. I've returned many tropical fish to the aquarium store when they outgrew my tank.
Like everyone said, you don't need to heat your pond for goldfish in LA. But, if you
want to put a heater in your pond
just to get your son off your back, you could drop in a
titanium aquarium heater (NOT a glass one!). It won't do much in an 800 gallon pond other than make your son feel better. It's gonna be on all the time, mind you, so the wattage is the wattage you'll be consuming 24/7. It won't do hardy any water heating (it will warm the water about 5-8" surrounding the heater, in my experience), but the fish can crowd around it if they want to and that should make your son feel better that they can do that and you'll have "put in a heater" (don't let it touch the sides/bottom of the liner, it can melt liners, secure it between a couple rocks). Mind you, he still can't be dumping tropicals in a pond and expecting them to survive winter. They are just going to die every fall unless you net them and bring them inside (I do this with my fancy guppies, I put them in the pond in the summer and bring them in when it gets cold). I run a 300 watt heater in my pond in Vermont all winter, it's really not a huge expense, it's just like leaving a couple floodlights on all the time, really, if you think about it. Just rig the plug up under something to keep it dry and be sure it's on a GFCI circuit since it's not rated for outdoor use. I've done it for 2 years now, no problems what-so-ever. I just do it to protect my pond liner from freezing/cracking because otherwise my pond would freeze solid up here (my pond is under 100 gallons though). I don't know how old your son is, but if he's innocent enough to think that tropicals can survive in a pond, then he probably innocent enough to believe that a 100 watt aquarium heater will work for your 800+ gallon pond and be happy that you "heated it".
