Pond Problems: Beat the Heat or Maximize My Oxygen?

We all know that Texas summers are brutal and this summer has been no exception: many days over 100 degrees and very little rain to break up that heat and replenish/cool down our water. Around this time of year, the epilimnion (top layer) of many lakes and ponds exceeds 90 degrees Fahrenheit! When our ponds are this hot, they hold less oxygen, which is the culprit for the majority of fish kills throughout Texas during the warm season. To combat this, we here at Blessed Bayou offer a host of awesome products designed for adding oxygen to your water and making your water less stagnant, such as surface aerators, bottom diffused aerators, and fountains. These three all have slightly different pros and cons, but I will get to that in a future blog post. Many pond owners for aesthetic and/or oxygen related reasons want to get or have already installed aeration systems in their lakes and ponds. In the summer, however, it is important to ponder the impact that this water movement has in your pond.

In times of stressful temperatures, fish seek places that are more thermally optimal for them just as we seek to stay in air conditioning as much as we can this time of year. The scientific term for these places is thermal refugia, which is just a fancy way of referring to a place that has temperatures that aren’t as stressful and extreme. This is why in the heat of a summer day, many people find it hard to hook up with a big bass in shallow water. During the summer, the deepest areas of your water body will hold the coolest water, meaning that bass will be staying there if they can. If you have bottom diffused aeration, your water in deeper spots will be well oxygenated, which is good news, right? Maybe not. You see, bottom diffused aeration systems create vertical water movement that breaks up the thermal stratification of ponds (separation of warmer and cooler water). In times of intense heat, this can mix that deeper cooler water, creating thermal uniformity in a water body. This means that fish could potentially not be able to escape 90 degree temperatures. Certain species of fish, such as largemouth bass with northern genetics, may be more at risk to temperature related mortality. Even those fish that can handle the temperature, such as largemouth bass with Florida genetics, are under stress in 90+ degree water, will not eat nearly as much, and will be more susceptible to parasites and infections in their compromised state.

So then what to do? Leave your diffused aeration on and risk a temperature related kill? Turn it off and risk an oxygen related kill? The answer comes down to your specific water body. If your water body is very shallow, with no areas reaching even 8 feet deep, you probably have water that is a fairly uniform temperature without much stratification. In water bodies like this, keeping bottom diffused aeration on is likely the right move since you won’t be robbing your fish of thermal refugia anyhow and your lake likely isn’t suited for thermally sensitive fish in the first place. If your water body is deep, it is best to consider if you have any thermally sensitive species in your water body that perhaps could die in 90+ degree water. If you don’t have any thermally sensitive species and you haven’t had a fish kill yet, the old adage of “if it ain’t broke, don’t fix it” applies here. But if you do have thermally sensitive species and/or if you had a fish kill recently in this brutal heat, it may be worth turning off your diffused aeration during the day. By doing so, you allow water to stratify enough to form more of a thermal refuge in deeper water during the day (when its hottest) and can pump air into the deeper areas at night. This way, your water in deeper areas strikes a great balance between keeping cool and staying oxygenated. If you are the owner of a surface aerator or fountain, this advice does not apply and you should keep those types of units on 24/7 during hot weather as those both pull water from the epilimnion and aerate your water without destroying the thermocline in your lake. Keep in mind that these are general guidelines and that we are just one phone call away if you would like our more personalized recommendations about how to find that balance between creating cool water and well oxygenated water for your specific water body.

 

Tight Lines!

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