Hi Everyone,

My wife and I are building a home on a 5-acre lot in Caldwell Idaho and we're
considering adding a pond for aesthetic reasons. We don't want to swim
in it or use it for fishing although it would be OK to have fish if it helped
keep the algae down.

The pond would be 40'x70'. The ground has a very slight slope. The soil
is very sandy and will not hold water so I was going to install a plastic liner.
I have access to an irrigation pump once per week that I can use to keep
the pond full.

It gets really cold here in the winter. Last winter it was -22 deg F and easily stays
below 0 for more than a week at a time. Not much snow though. In the summer
it's pretty darn hot. At times it is over 100 deg F for a week at a time. My initial
plan was to have it be 3' deep max which means it would get hot in the summer
and would probably freeze solid in the winter. This eliminates the possibility of
having fish to keep the algae/bugs down to a minimum. I could make it deeper
though. There is hardpan 8' down so that is the max depth I could go without
spending lots of $$$ to dig through it. I could use 1/10 of the water each week
to irrigate a small vineyard which would completely replace the water over a 10-week
period in the spring/summer. This is only true though if I keep the total size to
100k gallons or less.

* If the water is replaced every 10 weeks would I need to worry about algae buildup?
* If I make it 8' deep would that prevent it from freezing solid in the winter? Would this
could allow me to have fish?
* Would an aerator prevent it from freezing over completely even when the temp
is below 0?

Sorry for the long-winded post. I am a bit overwhelmed by all the information
available. I like the idea of having the pond as natural as possible and I don't
want to spend a ton of $$$ filtering it. Installing aeration would not be too difficult.
I was also planning on pumping the water through a small artificial stream/waterfall
near the house which is about 5' above the pond level which would flow back
down into the pond.

I would appreciate any help you guys/gals can provide on how to get started.

Victor

Hello and welcome. I can't answer all your questions and I'm no expert but from experience, aeration will keep your pond from freezing over. Mine is shallower and bigger and Wisconsin winters are pretty crappy and my aeration kept it from freezing solid. It will freeze almost solid but there is always a hole for air to escape.

If your pond was 8 feet deep and aerated fish wouldn't be a problem.

Victor, welcome to the forum! You will get your questions answered here.
I agree with pond dragon that 8 feet with aeration will be sufficient for overwintering fish in Canyon County.

I lived for nearly 15 years on the Snake about a mile upstream and across the river from Marsing in the '80s and '90s on the sole corner on Lloyd Lane. That was my first piece of property and I'm full of memories from there. I expected to build a pond there one day, but the sandy soil, and 350 feet of riverfront out my back door delayed my ever getting to the pond project.

Victor, welcome to the forum.

* If the water is replaced every 10 weeks would I need to worry about algae buildup?
Yes, at least the probability of having algae is greater than not if you don't have any other plants in the pond to utilize any nutrients in the water. It all depends on the amount of nutrients in the water and the water clarity. If the water is clear then yes, the algae will grow even if you bring in new water every week.
* If I make it 8' deep would that prevent it from freezing solid in the winter? Would this could allow me to have fish?
Yes and yes, but unless there is enough O2 for the fish to overwinter, then they might still die even if the water does not freeze all the way to the bottom.
* Would an aerator prevent it from freezing over completely even when the temp is below 0?
Yes and it would keep the fish alive too.

Anywhere sunlight can get to the pond bottom, AND there is enough nutrient nutrients, algae will grow. A 3 foot deep pond will grow more algae than an 8' deep pond if all the other variables are the same.

Plan for a 2-foot ledge all around for safety sake. You can use it as a plant ledge for hardy water lilies and such. Also check with your homeowners' insurance to make sure you'll be covered for liability.
Good luck.

Thanks for the feedback. Sounds like an aerator is in order. I can also add plants
to consume some of the nutrients that algae feed on.

If I don't stock the pond with fish will small fish end up in there anyway?

Victor

Yes, mine remained unstocked for at least 10 years and even without aeration brook sticklebacks and bullheads showed up. Thank goodness the bullhead died over winter.

Fish get in ponds from connectivity to stocked water, especially during flooding, and from people moving fish. Isolated ponds have stayed fish free for thousands of years.