Heating and Overheating and Supercooling Ponds by Erik Johnson DVM 

Overheating

 As we have mentioned before, warm water carries less oxygen. So, the times of year when overheating can occur are those times of year when it’s very warm and water temperatures exceed 80^oF

Of course, you can have dissolved oxygen problems at any temperature the fish are active in, just about. But above 80^oF  - you’re on thin ice. Overheating is not a condition of the FISH per se, but the observation that if you are NOT circulating the water VERY well, or if the pumps that circulate the water were to fail for a couple hours over 80^oF – the fish might very well die. You would notice, though, that the losses are very RAPID and they involve mostly if not only, the larger fish.

 Supercooling

 Let’s say you’re on a diet, like I am all the time. And you have some oatmeal with Splenda you want to cool, FAST. Of course you do, you’re starving after last night’s celery and tuna feast. When you want to cool oatmeal out fast, you spread it out on a paper plate. And blow on it.

Or let’s say you’ve quit smoking, so your coffee really achieves a sort of Godly role in the morning, and this cup is really, REALLY hot – you can pour it from cup to cup to cool it off. FAST.

What you’re talking about is a “thin phase” of the material, which dissipates or collects heat fast. So performs your waterfalls. And in Reno Nevada this can matter. Why? Because I said so. Next chapter now.

 Just kidding. The reason it can matter is because in Reno (for example) they have 100 degree days in May and 40 degree nights. It’s a “desert thing” they say. And anywhere this happens, you can see twenty degree swings in pond temperature in less than 24 hours. The pond gets toasty by day, and drops to ice at night. And fish hate it, the Stress Dynamic kicks in, and fish start dying of different opportunistic infections. In any part of the country, when you run the waterfalls through the winter, you can bring the temperatures WAY-y-yy-yy down. While a pond with minimal water turbulence (just an air stone and a cattle trough de-icer for example) might remain in the mid forties to high thirties – when you turn it all over and shove it through a waterfall on a snowy day, the pond will cruise down to freezing. Again, the Stress Dynamic kicks in, and fish start dying of different opportunistic infections.

 So, unless you WANT the pond to parallel the air temperatures prevailing by day or night, you should NOT run the waterfall during the less opportune temperature phases of the day or night.

BUT there’s a drawback to this. The fish, and the filter still require circulation whenever they are active. So you should have an alternative source of circulation, such as an aggressive air stone or a flooming pump to perform these duties without taking the pond’s water through a thin phase.