I have covered the importance of aeration and the use of an air pump in a pond in previous articles (see tags below). But today I learned a bit more detail that I thought needed sharing.
In light of the last few days of extreme summer heat, it is vital that the pond owner be aware of the oxygen levels in his pond. As water temperatures get over 78 degrees the water can not hold as much oxygen. This can create major problems for fish if you are not aware of the diminished dissolved oxygen levels. Seeing fish gasping at the surface may be the only indicators that a problem exists. The algae in the pond may provide some oxygen during the day but will crash quickly at night. Waterfalls in small ponds, or fresh water streams entering larger ponds can add some natural dissolved oxygen. Artificial aeration from an air pump will be your best bet. Even then a thunderstorm could knock out your pump and air pump and your pond would be left without the new sources of air. Few of us have back up generators for the pond.
Not only do fish need the oxygen but your nitrifying bacteria in your filter need oxygen to process the ammonia and nitrites create by fish waste. If the bacteria die, your pond can become polluted very quickly, which in turn will affect your fish.
Dissolved oxygen test kits can be found for around $50 for simple reagent test kits. Be sure to get one in the 1-12PPM range and not the 1-100PPM range. There are also Pen and Probe meters which are easy to use but are more costly ($300-$500). DO must be greater than 5ppm for fish survival. DO is around 9ppm at 70 degrees. At 90 degrees the most oxygen the water can contain is 7.5ppm and may be much less at night.
For emergency situations where you need to boost Oxygen quickly you can add Hydrogen Peroxide. H2O2 will release its extra oxygen atom. You should add in a non bio-filter or area away from the fish. Add 3% H2O2 at 1QT/1000 Gallons. If you have recently added medications like potassium permanganate it will halt their effectiveness. Keep an eye on PH level also.
Other Notes:
— You can add fresh cooler water (with declorinator) to help boost oxygen but do so at end of day so it doesn’t heat up in the sun.
— Your fish may be more active at higher temperatures and will want to eat more but over feeding them will create more waste. Clean your mechanical filters to keep water flowing effectively through the bio filters and let the bacteria feed.
— On really hot days provide extra shade over the pond.
— Reduce pond plants and/or remove some algae with a water change. Photosynthesis removes some oxygen at night.
— Watch fish behavior. If hanging at top in morning and bottom in afternoon then it may indicate you have low disolved oxygen.
— Add additional spitters, baki-showers, spraybars, or venturis to increase water contact with air. You can even point your jets upward to create a disturbance in the water.
