Pond fish dying in hot weather? "Fix it Now"

Pond fish dying in hot weather? "Fix it Now"

If you have bought goldfish or koi fish from Windsor fish hatchery we would like you to know how to look after them so your outdoor pond fish thrive. 

Ponds play a significant part in water gardeners' intimate interactions with nature and all of its pleasures. You are drawn outside by the sound of the waterfall, and once there, you are delighted to see colourful fish, attractive water plants, hear bird song, and enjoy your water garden. 

Summer heat and other activities can cause major problems in your pond. Read the checklist and fix problems before they affect your fish 

Why any one of these things can cause major problems in your pond over summer

  Over crowded pond

  Poor quality food 

  Lack of Beneficial bacteria  

  Shallow pond less than 40cm in full sun

  Murky water

  No water movement 

  Excessive Algae

 high ambient temperature

 low pH

 Decaying leaves and debris

 leftover fish food in the pond

 High phosphate levels in the pond water

How to Oxygenate a pond quickly "fix it"

Temperature- Warm water loses its capacity to hold onto oxygen particularly at temperatures above 29 degrees Celsius. Warm water combined with poor water circulation can create pockets of oxygen-depleted water harmful to pond inhabitants.


For a shallow pond in full sun drape or fix shade cloth over the pond & add an extra pump for more water movement.

Biological load- Simply put, more pond inhabitants mean greater demand for oxygen. Poor quality food will cause more phosphates & organic material within the pond to complete the process of breaking down organic waste good bacteria needs oxygen, heavily stocked ponds can deplete the existing oxygen supply.


 Do a water change 20% at least daily in extremely hot weather and weekly in temps up to 30 degrees. Reduce the load by feeding a better quality fish food. Cleaning out debris from the bottom of the pond

  Always feed high quality food, to keep your water at its best, & low phosphates fish food Saki Hikari food is new for us this year 2022, we have had amazing results for both the fish & the water. The fish seem to absorb every last bit, with the least amount of waste going into the water. You feed less to get better results.

Test your pH and Phosphate levels

TEST pH regulates how much oxygen is available to your fish, a pH of 7-5 to 7-8 is preferred for pond fish. 

TEST Phosphate levels are directly related to the pollution in your pond, when they are too high your pond wont be stable, you may have dirty water, sludge on the bottom, algae, green water, debris floating on the water surface, dying plants, dying fish. 10.mg/1 is the highest level that is expected in a backyard pond. 


If the pH is below 7-5 bring it up slowly over the next week with pH up in liquid form or bi carb from the supermarket. Bi Carb dose is grams per 1000ltrs to 5000ltrs if your pond is bigger than 5000ltrs text or email the hatchery for the dose. Test daily till you have the correct pH by adding bi carb in the morning and testing the next morning.

FIX IT phosphate

Do a water change of up to 50% depending on the amount of phosphate in the water. for more information on understanding test results read the blog. water testing kits australia

Water Clarity- dark, murky or turbid water can limit the ability of plants to photosynthesize & generate oxygen.


maintain clear water for healthy plant growth essential for natural oxygen production.


Surface exchange - Encourage proper gas exchange by keeping an area of open water. This open area should be free of vegetation so surface water is exposed to fresh air.

Mixing - Water turbulence of any kind, regardless of how it's generated, significantly increases gas exchange. The fastest, easiest way to raise the oxygen level in your pond is a water change or with an aerator, fountain, or waterfall.

Evaporation of pond water

Be aware of pond water evaporation. Up to 4 inches may be lost each week. Check for a pond leak if you're experiencing anything more than that. Top up and remember to use water ager to neutralize chlorine so you dont kill your fish or your beneficial bacteria 

One of life's tiny pleasures that you want to enjoy as frequently as possible is the beauty and tranquilly of your own water garden.


Windsor fish hatchery breeding and selling Koi & Goldfish since 1984