Storm Warnings For Ponds

California has earthquakes; we in the south and east coast have hurricanes. One thing we all share is power outages. Ours are usually caused by storms. Most power outages last only a few hours and only happen a few times a year. A hurricane is always a threat that hopefully will never happen or have only a minimal consequence. Flooding may be more common then a power interruption and both can happen at the same time.

A well built well thought out well designed pond will survive a big storm with a long power outage, lots of rain and flooding. This pond also will be less worrisome during the numerous smaller but strong storms. The most obvious and the most popular is the garden pond. It has few fish so it does not need extra filter or aeration. There is enough surface area for oxygen levels to be sufficient. The surfaces of the pond and plants handle the filtration. A koi pond should be able to stand-alone for hours without danger of quick suffocation or toxic waste build up. The key is in the number of fish. Conditions in an over stocked over fed pond will quickly deteriorate. A lesser or under stocked pond will always be healthier, have less maintenance, and survive periods of no power.

Heavy rain can make a pond quickly overflow or be flooded out. Heavy rains can cause a rapid change in the pH and the temperature of your pond water. Check your inventory of chemicals such as pH adjustors, Amquel or Ammo Lock. Heavy rains can cause a change in the pH and the temperature of your pond water. Water with higher alkalinity will have a stable pH. Buffers can be used like baking soda will help keep ph stable. If it is possible use a tarpaulin a few feet above the surface to permit airflow yet keep rains out.

A pond should be built with the top above grade. Six inches is minimum and twelve inches is better. This can be a raised wall or lip. It also can be graded out and still have an in ground look. This will make rainwater drain away from the pond instead of into it. Choosing a spot that is not the low spot that always floods should be avoided or built higher. ? If at ground level consider surrounding the perimeter with a wall of sand bags 1 or 2 bags high. Drastic, but it has been done. This may protect your fish from being washed away and never to be seen again. Is it possible to set up a portable show tank, maybe in a garage or other protected area? We know that with changes to their environment, Koi will often jump. Murphy says that they will land in the worst possible location. A net surrounding the edge or covering the pond is therefore advisable.

An overflow drain is easy to build and may be the most used and important design of a pond. Without an overflow the water level will never be constant, be hard to maintain and get too high during a storm flowing over the top. An overflow drain should be large enough to handle large amounts of water I like four inch pipe. It can be above the waterline or stubbed up from below. It needs to drain to an area that can handle a lot of water. A storm drain, a dry well or a drain field, which is a large hole with gravel in it, then covered work well. Making a bog area where the overflow water goes also works. Just take care that it does not flood someone else. Having the waterline above grade makes any overflow drain simple.

Lower stocking and overflow drains are simple ways of making a pond storm proof but there is more we can do. Most of us like to be heavily stocked with more fish then we should have. We may not want our fish not to have periods of low oxygen or risk an ammonia build up. One solution is to have an emergency generator that can be started automatically when the power goes out. They may not be too expensive for the piece of mind and convenience they provide. A portable generator can be used for some or all your equipment but will have to be started and switched usually during a storm. Both of these solutions work but will need fuel on hand and tested regularly for events that may only happen once or twice a year or a big event that may never happen.

Lets say we are in a hurricane watch or a tropical storm warning and we have five days to get ready. There are a few simple things you can do and a few simple items you should have on hand that could save your fish until power comes back on in a few days.


Koi will be fine for a week with no food. With no food the amount of ammonia produced will be dramatically reduced. This is a common practice when taking koi to a show to prevent ammonia build up in holding tanks. Koi excrete the most ammonia right after they eat so if bad weather is approaching you may want to skip a meal. The longer the better. 3-5 days of no food will make a huge difference.


Products like Amquel or Ammo Lock are products that bind ammonia and prevent it from harming fish. These products should be on hand normally. You can test your water for ammonia and use these products to control it. Make sure your test is a salicylate type as opposed to a Nessler rent base kit that will give false readings with ammonia control chemicals. Mydor is one brand of test kit that will work.


Storms happen during the summer when it is sunny and hot. A tarp on PVC legs or rope over the pond will help keep the temperature down. This will help keep the dissolved oxygen up and make the fish more comfortable. With no power or air conditioning it may also be a nice place to be. I have seen some inexpensive quick garden shade canopies that could be used.


A car battery and a power inverter can run an air pump and air stone for hours. The battery can be kept charged with a charger on low and a timer so it is not charging all the time. When the power goes out you plug your air pump into the inverter. Aeration using this method is very efficient, low in cost and easy to do. You may have these items already. For longer periods of time you can recharge the battery with a car, self start lawnmower, motorcycle or small emergency generator. You also can find complete units like the XP600 for $279.95 from Aquatic eco- systems. Small emergency generators are good on fuel and can provide many hours of aeration.


This is another item that should be on hand. It can be added to the pond and add huge amounts of dissolved oxygen to a system. Simply use to 1 cup per 100 gallons. Apply with a squirt bottle forcefully under the surface of the water. 60 squirts is good for 100 gallons


Bacteria in a filter will go anaerobic without oxygen. It will start going bad and producing toxic wastes like hydrogen sulfide. A few hours may be ok but if the power is out for more than a few hours you should not pump right back into the pond. You should back wash your filter first. If it is an open filter you can have air stones on your emergency power to help keep the filter aerobic and living.


Make sure that all equipment is grounded with heavy wire and GFI protected. This will lessen them being damaged by lightning, storm surges and shorts from wet weather.

This is only intended to be a brief guide and in no way details all steps that can or should be taken in an event.

In summary plan for flooding and power outages. Do not to over stock unless you have the equipment to support a livable condition. Plan for ammonia build up with no filtration by chemical treatments and halting of food. Emergency power works most efficiently with aeration. Most storms are short or do little real damage. Having a plan to handle them will make life less stressful for you and your fish.

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About The Author

Brett Fogle is the owner of MacArthur Water Gardens and several pond-related websites including and He also publishes a free monthly newsletter called PondStuff! with a reader circulation of over 9,000 pond owners. To sign up for the free newsletter and receive a complimentary 'New Pond Owners Guide' for joining, just visit MacArthur Water Gardens at his website.

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