That heater will add from $35 - $50 a month to the electric bill. At least thats what mine cost before I stopped heating and brought the fish inside for the winter.
I have had ponds in various forms, most recently in an old wash tub about the size of a half whiskey barrel. It didnt need a liner, and that's the only flaw i can see in your plan. One pond liner i had was a very stiff plastic, would have been hard to fold into a small enough sizeto fit in a whiskey barrel. Plus those folds build up gunk quickly. For something that small, you'll want it in the shade if you want to keep it from growing algae and keep the water temp okay for plants and fish.
Winter is an issue...i had a goldfish in it one summer, he got pretty big and i didnt have anything to bring him inside in...gave him to someone with an aquarium, and, um, he took some horrible funk to all her other fish and they all ended up dying. Oops.
I've played around with lotsa different bubblers and spitters and cascading down through pots or even up through an old coffee maker (its hard to explain!). I even had a mini japanese bamboo "clacker" - the water dumps into a section of bamboo and when it gets full enough, the section dumps into the pond with a loud CLACK. I loved that feature, but it took a lot of fiddling and adjustment on water pressure to get the right flow. I would use zip ties and partially close the hose between the pump and my feature to reduce water pressure, but there's no way to increase it - if your pump doesnt push enough to make your feature work, you end up buying a bigger pump. (i think i have 3 different ones around somewhere!) also, clear water hose builds up algae faster than black (duh )
Anyway, have fun. I'll have another one next summer probably in the wash tub on our deck again...someday maybe a big in ground one again also.
That's exactly what I was going to use. It's a molded rigid piece that drops right in. No seams.
They also make them with a spillway so you can fill your barrel and intentionally have it pour water where you want it to go without having to cut into the rigid liner or the barrel.
This was just the first one I found when I searched to give you an idea I what we're talking about.
I'm not 100% sure what the plan is for the winter yet. Part of me is ok with taking it down in the winter when the frost comes and wintering the plants and fish inside the other part of me is tempted to try to see what I can do with hibernating them.
Worst case is I tear it down every late fall hibernate the perennials and the annuals are composted.
Part of me is tempted to raise a fancier variety if goldfish so if they make it till the frost rolls in I might be able to rehome them easier. Little more demand for larger fancier varieties than say oversized feeders.
Just a note of caution ... when using a half barrel and installing a liner... if no water comes in constant contact with the barrel boards, they will eventually shrink to the point where the bands fall off and then what ... ?
@bobm ours did that. No problem! The liner has a lip over the top edge holds boards upright while you slide the band back up and tack in place with a few short nails or screws. (Just so they are not too long and puncture the liner.)
@Carol Dee how long did that take for the bands to slip?
Wondering if I should do a little "preventive maintenance when the barrel is first empty. Probably do some copper nails so as they age it only enhances the barrel.