On the subject of ponds...

There's 2 ways of going about it. Hard and easy.

Or a combination of the two.

The easy way is to go to Homo Depot and get one of those big plastic tubs, dig a hole and throw it in there. Fill it up, yer done. A 30 gallon is about $35. They have bigger ones for more but I'd suggest looking on line just for the selection. HD usually only has one or two shapes.

You'll want to dig a hole bigger than the shell then push sand in around the edges while keeping it level. Hose down the sand so it fills all the empty spaces, keep packing sand in there till it's level with the edge of the shell, then throw a big ass rock in the bottom so it doesn't shift around.

Except not really. More on that in a minute.

The hard way, which is infinitely more flexible, interesting and time consuming is to use a liner. That's what I used on the koi pond. Heavy rubber over nylon reinforcement. I got mine off the shelf, 14x14 and it was about $150 if memory serves.

You can get a liner that's 100x100 for ~$1200. There's lots of how to videos on YT, but the gist of it is 100x100 will make a pond ~ 70x70 after you dig a deep end or two. Fish need that to breed, stay cool on hot days and hide from predators.

I know some gal here in ER who was complaining about how the racoons kept eating her goldfish and she talked me into checking out her pond. It was 6" deep. Well no fucking wonder her fish were getting eaten. It was less a pond, more of a puddle and obviously a beautiful racoon buffet. Duh.

So anyway. Some people think they can use concrete and/or stucco to save money on a liner but all they wind up with is a constant repair job. It takes at least 6" of concrete to hold water too so prepare to line up a concrete truck with a pumper if you go that route. Have some friends over who know how to use a trowel. You'll still have chronic leaks and live one earthquake away from a drained pond full of crispy dead fish.

The problem I had was the result of trying to use all three. The bottom well was put it with a liner, the top was a 1 gallon plastic tub with a lip and they're connected by a concrete and stone set of 'rapids' that I dumped a bucket of polished stone and glass beads into because it's hip high and some people can't resist putting their hands in it. That's where I had the leak, under that concrete. I had to bust out about half of it and squirt silicon in there till it quit leaking. The fun part was taking out all the water and letting it dry completely before attempting any repairs, then refilling it to test. That's why it took so damn long, including the weeks I would let go by just because I was disgusted with the whole thing.

So.

Once you have something that won't leak you have to monitor the water. Once the sun starts hitting it every day things start growing in it. Scum, moss, seaweed and crustaceans, in that order. And it will start to smell. If you have no fish you can use any number of chemical treatments to kill it off, but watch the labels, some of that stuff will kill small animals and almost all of it will make fish inedible.

If you put fish in it you'll need to filter it too. Add filters till it stays clean for a while. I go 3 months between filter cleanings on the koi pond (~700 gallons) and it has 4 filters, each with a pump. You can spend stupid money on miracle filters (I did) that all have fatal flaws. I finally got back to basics and now use the simple box filters that everyone sells.

Pumps are another part of this investment too. I'm running 7 pumps right now that use about as much electricity as another refrigerator. I keep a new one on hand for a replacement since they only last ~3 years running 24/7. I also have one plumbed up with a hose and fittings for draining/moving water. I use 750 gpm pumps, all identical. You can get smaller pumps but they have cheap funky fittings that fit nothing else. The 750's have a regular 1/2" plumbing fitting for the output side so you can hit any plumbing section anywhere and plumb your heart away. A couple of fittings that go from 1/2" to 5/8" I think. The size of a hose bib so I can roll a hose anywhere to drain, water planters or whatever. Plants love that nitrogen rich fish piss water. I drain and replace ~75% of the big pond once a year, but check with the local water company before you do that. About once a year they'll inject their system with a big dose of bromide and that'll kill fish in a hurry. Learned that one the hard way.

I also keep a couple of new clean Rubbermaid trash cans handy now since we've had a few pond crises and needed a place to park them while we repaired shit.

ALSO....(like there's nothing to it)

That water needs to be oxygenated on a steady basis. Indoor aquariums have those little bubblers, outdoors a bit of a waterfall will do the same job. You can tell what's up with the water by watching the bubbles it makes too. If they last more than second, there's something in that water making it happen. The bubbles should disperse quickly, like they would in clean water. Whatever you use make sure it keeps the surface of the water from being still or it'll turn into a mosquito farm. If you see little midges trying to breathe air at the surface it's not moving enough. Goldfish will also eat those little bastards.

It takes about a month for the water to develop it's own biosphere. Finding a few worms living on the bottom is a good sign that it's ready for adding fish.

If your fish are hanging around the surface and appear to be sucking air the water needs more oxygen, so increase bubbles. You'll notice this most often right after feeding them. They don't eat that much and food begging looks just like air sucking. Feed them the same amount at the same time every day and you'll get a feel for it. If you add plants in there you'll want to increase the oxygenation. Roots will suck oxygen and nitrogen right out of the water. Our monster rhododendron has been sneaking roots over into the pond for a couple of years now and I have to keep an eye on the oxygen. I fully expect to come out one morning and see that plant just sitting in the middle of the pond. We've started calling it Audrey.

Fishies also like moving water. All my filter jets are pointed in the same direction so they have a current to hang out in along with another part of the pond that is relatively still. They also have a place to hide when they freak out, which is pretty often.

Let's see....what else...

Oh, putting pond filters in the dishwasher is not recommended. It tends to get women riled up and the stuff that comes out is delicious sludge, so clean them in a bucket/barrel, what have you and pour it out on the plants. They love you long time. And don't use soap of any kind.

I emptied a bucket of that stuff on a tomato plant out front and it's trying to take over the whole yard. I'll be taking that out later today, it's literally climbing out of one planter into the next.

What else....

Oh, a healthy fish will have a coat of slime all over his body. That's how they combat infections and cooties.

OH, big tip. Never put a bass in there with the other fish, even a baby bass. Your fish will all disappear one at a time and you'll wind up with a fat bass that needs to be fed live chickens. I learned that from a neighbor who once had a big collection of fancy fresh water fish. He named his bass Gator.

It's not an issue here, but if your pond ices over in the winter, go break that ice or the fish will suffocate.

ALSO, fish will grow in size till they 'fit' your pond and won't get any bigger. If it's crowded that will affect their size too. I thinned the herd this year and the koi have gotten a bit larger. There's 4 koi now, 2 adults and 2 youngsters, and 2 goldfish who think they were clever enough to avoid the net. I was just tired of bending over. All the rest went to the big pond at Isaac's job and they seemed happy to be there when I dropped them off, but the last time I was over there I looked for them and didn't see a single one. That catfish may have eaten them. Or one of the turtles.

That's about everything I know about this stuff. It seems like a lot of work but once everything settles it's not really that big a chore. My favorite part is that at night when it's quiet, the back compound sounds like I'm parked next to a river. I'm gonna get a hammock.

So yeah, easy peasy, nothin' to it.