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…

IMG_20180815_183451557

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!

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