Garden Pond Water Temperatures

Water Temperature Can Be A Cause of Fish Stress

Don’t Stress Out Your Fish!

Whether your garden pond is 75 gallons or a wonderful (yes I am jealous!) 5000 gallons, being aware of it’s pond water TEMPERATURE is very important. That is if you want plants or even more importantly, ornamental fish, such as shubunkins or Koi to live happily.

Note: A handy Fahrenheit & Celsius temperature converter calculator is located at the bottom of this article.

Think about it. If your pond water temperatures get almost to the boiling point during the day, how will delicate plants or even more delicate fish survive? The water doesn’t have to be “too hot” … if you stick your hand into your garden pond and it is way too warm for what you’d consider “comfortable” … then it is probably WAY TOO HOT for plants and fish!

Invest in a Floating Garden Pond or Spa Thermometer

Let me cut right to the chase. I’ll make this really easy … go and buy yourself a pond or spa (hot-tub) thermometer! It doesn’t have to be fancy. As a matter of fact, the one I use for my Koi pond is a floating plastic one, which I found in the garden department of a “big box” DIY store. I found it amongst the hot-tub and swimming pool chemicals and supplies. I paid around $5.00 for it. It has lasted me many years.

Please do yourself, your plants and fish a favor … purchase a floating plastic thermometer.

Oh, please don’t use glass ones like those used in aquariums. Not only is broken glass not good in a pond environment, but Koi have been known to swallow these small thermometers!

Smaller Ponds Cause Faster Changes

Temperature Swings Become Less Dramatic The Bigger The Pond

The Smaller The Garden Pond’s Gallonage The Bigger The Temperature Swings

I think you can probably visualize that the less water in a pond, the faster the water will be able to heat up or cool down. And rapid cooling will be accelerated if you have a waterfall along with a very small pond. So, being able to monitor the temperature “swings” of your pond will become important.

This becomes especially so (to repeat myself) if you want or have fish. Here are ranges that pertain to ornamental fish:

Temperature Ideal Range 65°F – 75°F (20°C – 25°C)
Acceptable 35°F – 85°F (2°C – 30°C)

I will hope that as far as garden water plants are concerned, your common sense will dictate that temperatures such as 35°F (2°C) will be too cold for any plant to survive.

A Garden Pond’s Temperature Will Normally Follow That Of Its Surroundings, With The “Swings” Becoming Less Pronounced In Relation To The Size Of The Pond

Things like a pond without shade, with the beating sun shining upon it all day will certainly make for a more rapid temperature gain, than a pond that does get shade for a number of hours every day. Clear nights can cause a quicker heat loss to ponds, believe it or not. There are many variables other than garden pond water gallonage to take into consideration.

Problems Arise Quicker in a Smaller Garden Pond

I am sorry if you are reading this and have a “small” garden pond, but it is a fact that negative events/problems generally happen faster at higher temperatures and in smaller ponds.

I won’t go into all the detailed scientific data (maybe that will be for another article) however as an example, the toxicity of ammonia increases as the temperature rises in the pond water. And in direct correlation to this toxicity issue, the amount of dissolved oxygen that the water can hold decreases. This is double-jeopardy to any garden pond fish.

So, if at all possible, decide to dig your garden pond as large as possible IF you really wish to add fish. If it is just a lovely pond with all sorts of water plants you desire, then remain aware that you want enough gallonage to allow reasonable high and low temperatures which will facilitate healthy plant growth.

Here’s a neat little temperature converter tool that might come in handy for you   🙂




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