Garden Pond Part 3

Part 1 and part 2 detailed some of our garden pond work. Now it’s time to add some fish to this fish hole! Currently we have a handful of goldfish that were originally for mosquito larvae control. They’ve been doing pretty well and getting bigger just eating bugs and algae. We’re not sure when we’ll add more or what we’ll add, we’re taking it slow!

The pond is about 40″ deep when full. According to various books and websites, this *should* be sufficient for hardy fish like koi and goldfish to overwinter. We will likely add a heater and/or aerator to maintain a hole in the ice. We’ve put various artificial caves near the bottom so smaller fish can hide out and (hopefully) avoid getting eaten.

Another addition is something I’m calling the fishdome. These are also known as inverted aquariums or fish observation towers.

Essentially it’s a bigger version of inverting a cup in your sink and pulling it up to trap water above the normal water surface. The ambient air pressure above the pond holds the weight of the water in place against the negative pressure inside the sealed container.

An article on the physics of this can be found here: https://www.wired.com/2016/12/not-impossible-fish-tank-just-physics/

And a video demonstration of how to do this is here: https://www.youtube.com/watch?v=0njOh04cUOU

Incidentally, we didn’t really plan this fishdome thing… it came together as a result of hoarding and wasting time on the Internet. I had previously dumpster-dived a giant Pyrex bell jar, simply because it looked cool and with no plan for what to do with it. Later I came across the video above, and realized what we could do with the jar!

The dome rests on a stand made from ABS pipe. I love working with ABS and PVC, it’s like giant tinker toys for adults! I think some of my favorite uses have nothing to do with plumbing…

Shopping for stuff like this definitely confuses hardware store clerks. No one can seem to understand why I might want a 4-way 2″ ABS tee with identical sides or a 3-way 90-90-90 elbow… Since those things don’t seem to exist, I had to make do with the design above using 8x 90-degree elbows, 8x sanitary tees, and a lot of straight pipe. Everything is epoxied together so it won’t wiggle, and I drilled some holes in the final creation to let in water and help it sink. It also has some sand ballast in the bottom so it won’t float away while I set it up. I also added some bolts at the top to keep the dome in place and prevent it from slipping off to the side.

The dome does tend to get a little scummy inside, as algae grows on the inside of the glass. I’m hoping that the addition of more algae-eaters will help with this. For now I just take it out and scrub the inside if it gets too bad. I plan to remove the dome once it starts getting colder, as I doubt it would survive freezing.

Having an open body of water in the yard has immediately attracted more wildlife. We have more birds than ever visiting the garden, and the local toads and frogs are attracted to it as well.

Another update is that the pond seems to have all major leaks taken care of. Previously I had an intermittent leak that would come and go, which made locating it very frustrating. After reading about the possibility of wicking/siphoning around folds in the liner, I added sealant to all the major folds. This seems to have done the trick, as the water level is much more stable! I’ve also adjusted the edge a bit more to try and divert overflows to a specific side, and to make rock edging easier. Next up is re-laying all the flat limestone rock around the perimeter!

Since limestone can leach into the water if submerged, I’m trying not to put any directly in the pond. We’ll probably be using other rocks to create fish hides and hold underwater planters in place. Those updates will show up soon in a future post!

Garden Pond Part 2

Part 1 of this project covered some initial construction of our garden pond. Now it’s time for some photos with water!

The pond and swamp pool take quite a bit of water to fill! I haven’t calculated the exact volume, but between the 300gal and 150gal stock tanks, plus liner extensions, and minus filter media, I’m guessing we’re in the ballpark of 500 gallons. We’re trying to avoid any chemicals to that might stress the fish, so most of the water comes from our rain barrels.

According to various websites, moving water loses about 0.5-1% per day of the total gallons pumped per hour, so we’ll have to occasionally top this off to maintain the water level. We’re pumping 1000gph so can expect to lose something like 5-10 gallons per day to evaporation. Another way to calculate water loss is based on an archaic government-issue kiddie pool. It’s all a bit fuzzy and dependent on surface area, cloud cover, and humidity, but after eliminating any detectable leaks we’ve noticed water loss consistent-ish with both these measurements (about 5-10 gallons per day).

The smaller swamp filter pond is a little higher in elevation than the main fish pond. As mentioned previously, “dirty” water gets pumped from the fish pond into the bottom of the swamp, where it percolates up through gravel, screen, and mud. To get the filtered water back down, I could have done a stream or waterfall, but decided to do a canal instead. Naturally a canal needs a set of lock gates to allow boat navigation between the different water levels!

The lock gates are hand-operated, and work pretty well. They aren’t particularly watertight, so enough turbulence and splashing develops to help aerate the water.

The swamp pond has a miniature dam with some extra filter media behind and below it, to help keep mud from migrating out of the swamp into the main fish pond. So far there’s been a little mud slipping through, but it clears up fairly quickly. I imagine we’ll have to clean things out and relocate the dirt periodically.

As I’ve probably mentioned in other posts, we have some pet waterfowl (ducks and a goose). While they’ve been quite interested in the process of digging this pond, we’re not planning to let them use it. Ducks are just too messy and destructive for a small fish pond like this. They rapidly pollute the water, tear at the liner and plants, eat the fish, and drill holes everywhere with their beaks in search of bugs. Our birds have their own private pond with an oversized filter, which I’ll detail in another thread.

Apparently the local wildlife hasn’t heard about this “duck-free” idea, as we’ve already had a wild mallard hen land in the garden for a swim!

In the next update we’ll try to make this hole in the ground look prettier and add some actual fish!

Garden Pond Part 1

This summer we decided to build a garden pond. I figured we could do it “simple” and “quick” using plastic livestock water tanks… but it has become a bit more complicated over the course of construction! Below is the final-ish plan for how our pond is set up. It includes a main, deep pool for fish, and a second pool mostly filled with various materials to act as a natural bog or swamp filter.

This design is based on a combination of sources, from pond books to internet forums to various other info. While it may not be the best/cheapest/simplest method, I’m hoping that it will manage to combine natural filtration, low-ish maintenance, and an interesting look! The main fish pond should be deep enough to over-winter fish in Minnesota, perhaps with the addition of a bubbler and/or heater.

Transporting stock tanks is always entertaining…

After extensive planning, we started digging the holes.

Thanks to some research, I had already determined that our garden used to have a duplex in the 1800s, which was at various times home to a saloon, an election polling place, and a local con artist. While digging the smaller hole, we ran into the limestone foundation.

I dug up an entertaining array of artifacts from the old rubble, including bottles, pottery, coal, a narrow-gauge railroad spike, a knife blade, and an empty .38 revolver casing!

After getting the holes finished it was time to install some plumbing for the pump and filter system. I added heat tape to the pipes since there’s no easy way to drain them. The pump will probably stay turned off in the winter and I have a thermostat-controlled switch to turn on the heat tape if the ground temperature drops too low.

The pump is also located underground in a waterproof box. This will eventually have a bench on top of it.

Next came the stock tanks. The pond holes ended up quite a bit larger, as we decided to just use the tanks as the bottom of the pond and extend everything with flexible liner. This might be a bit redundant, but it does make the bottom few feet of pond extremely leak-resistant!

Getting a square liner to fit an oblong hole is a hassle, and results in a lot of unsightly creases. I did my best to reduce or hide these, but still ended up with some ugly folds (pic below is not the final liner arrangement).

The bog filter received a plastic shelf raised off the bottom with brick (which is safer for fish than cinderblocks or limestone, which can leach lime into the water). Below the shelf is a PVC diffuser for incoming “dirty” water. Above the shelf goes gravel and dirt for the swamp in various layers. The two pipes at right are cleanouts to help deal with the inevitable mud that will make its way into the bottom void area.

Coming soon, some more details and photos with actual water in the pond!