Summer Rain & Drought

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Summer can mean a lot of different things depending on where you live. Especially in North America spanning from a rainy hurricane season, a late, sometimes non-existent Spring that moves right into extreme heat or extreme dryness.

All of these factors can cause problems for your pond if you don’t take the right action. Hot and dry conditions can lead to evaporation from your pond. A lower water level can throw off the balance of nutrients in the pond, so if too much water evaporates you should refill the pond. 

It’s important to ensure any water you add has been appropriately treated, especially if it’s been chlorinated. Also remember to account for evaporation when you do water changes. Rain can provide a free, source of water to top off your pond, but it can also dump pollution and acidity into the pond. Additionally, any type of rain can wash lawn chemicals and fertilizer, leaves, grass clippings, and other forms of debris into a pond. This is especially important for those living in extreme summer weather states where hurricanes are commonplace.

“In my experience, too many people believe that topping up a pond due to evaporation, and allowing rain to fill a pond is equivalent to making water changes!”

-Isa Webb, The Bloomin Bog Water Gardens

acid rain pond

Ponds located near industrial sites, coal or oil burning power plants, and highways run the risk of being affected by acid rain. If you live in an area known to get acid rain, there are several things you can do to keep your fish happy and healthy. Always scoop out algae blooms after it rains, and remove any debris that wash in during a storm to help keep the pH balanced.

Check your pH regularly to help you stay on top of your pond’s performance. To protect fish against acid rain, keep the pH balanced and dissolved oxygen levels high. pH Measurement Tips:

  • Algae raises pH during photosynthesis and lowers the pH during respiration.
  • Your pond changes pH throughout the day and is lower in the evening or early morning before sunrise.
  • Fountains, waterfalls, and circulating pumps will aerate the water and reduce how often the pH changes.
  • The pH range should be 6.5 to 9.0. Fish can become stressed in water with a pH ranging from 4.0 to 6.5 and 9.0 to 11.0. Fish growth is limited in water with pH less than 6.5 and reproduction ceases. Fish risk death at pH less than 5.0 and stand almost no chance at levels under 4.0 or greater than 11.0.


The pH will be lower when algae dies off. Whatever you do, do not try to reduce the pH using pH-reducing chemicals, acids and the like. In backyard ponds this often causes a pH “crash” that could kill the fish.

When summer heat kicks up a notch, many people will experience dropping water levels. It’s common to lose as much as 1 inch of water each day due to evaporation and as the heat increases, so does the water lost from your pond. With this in mind, it’s important to remember the above advice when topping up your pond. Always ensure the water is properly treated.

For example, well water generally has little to no oxygen but can be high in dissolved matter which can be harmful to fish. This is where pond aeration comes into play.


“It has taken a few weeks, but in conjunction with UV filters, and an added screen roof, the water in my 2500gal koi pond is very clear. In the Arizona low desert, this is almost a miracle. Thank you, Nualgi. :)”

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