Why do Fish gasp at the surface of the Pond?

If you see fish gasping at the surface of your pond, this is cause for concern. You should investigate.

Fish gasping at the surface of your pond requires immediate attention; they are not greeting you, but they are telling you that there isn’t enough oxygen in the pond water or the water quality desperately needs attention.

Signs of Poor Aeration

If you see any of the following signs, your pond will need extra oxygen:
• Fish gasping at the surface of the pond or at any entry points for water (Waterfalls, fountains, streams).
• Foul odours - decaying organic matter (Fish waste, plants, sludge) can indicate that there is a lack of oxygen, water movement or filtration.
• Rapid algae development - This can be a sign of poor aeration and filtration.

Why does lack of aeration lead to an increase in Sludge?

When your pond is properly aerated, the healthy bacteria in the pond will help to naturally break up and remove the sludge. If there isn’t enough oxygen in the pond then the healthy bacteria will not develop and if this does not happen, the sludge will build up and this can have a huge effect on your pond. Please see our Pond Sludge blog for more information.

You can always add extra healthy bacteria to your pond using the PondXpert Gel Balls and Evolution Aqua Pure Pond Bombs, or you can add the bacteria directly to your filter using the PondXpert Filter Start Gel or the Evolution Aqua Filter Start Gel.

Low Oxygen Levels

In short, the low oxygen levels can be caused by several reasons. Below, we have listed the main reasons for a lack of aeration.

Temperature: In short, warmer water holds less oxygen than cold water. This means in summer, your water will hold less oxygen. Add to this the increase in fish metabolism in warmer weathers, your fish will require more oxygen. More information on this dynamic can be seen on our Temperature blog.

Pond Size and Fish: Bigger fish will need more oxygen than smaller fish. So if you have Koi, you need to add extra air! Sturgeon are also considered to be ‘oxygen hungry’ fish. Plus, the more fish you have, the more oxygen will be used up.

Lack of Plants: If your pond doesn’t have any pond plants in, this is a serious issue and needs to be resolved. Plants add a huge amount of oxygen into the pond and help to curate the chemicals in the water. We always recommend 50% plant coverage in the pond.

How to Aerate your Pond

There are several easy, long term resolutions that you can embrace to keep your pond well oxygenated, and therefore healthy. Please see our blog posts on aeration for more information.
• Install an air pump into your pond; this is the most efficient way to aerate your pond.
• You should add pond plants, which aerate the water during the daytime. However, if your fish are only gasping at the surface on a morning, it could be that you have too many plants, as plants suck the oxygen out of your pond at nighttime.
• You could also install a Fountain or Waterfall, as these keep your water moving and they disrupt the surface of your pond, which helps to oxygenate it. These should be turned off in winter, as they can freeze over and cause water loss. 

Poor Water Quality

Poor water quality can contribute to fish gasping for air at the pond’s surface, so check your filtration system and test your water using the Tetra 6-in-1 Test Kit or the Blagdon Pond Health Test Kit.

When we say you should check your filtration system, this includes several small checks. Including if you are using the correct filter system.

If you have fish, your filter system should be filtering your pond once every hour. If you have Koi, you need a box filter; if you have Goldfish, you can use either a pressurised filter or a box filter.

Further to the above, how often do you clean your filter? You need to make sure there isn’t a build up of sludge, else this can negatively impact the pond and impact the oxygen levels. Also, check your UV bulb to see if it needs to be replaced.

Green Water, Blanketweed and Duckweed

If your pond is covered in any of the above, then your pond will naturally hold less oxygen. The reason for this is the algae that causes the green water, blanketweed and duckweed all use up oxygen. These are big competitors for the oxygen in the pond. See our Pond Problems blogs to see how these can be prevented and treated.

What size Air Pump should you use?

We have provided a guide below on the size of the air pump you should use. The size of the air pump depends on what kind of fish you have and the size of the pond. Please treat this as advice only, every pond is different.

If you need any further assistance, please email us on info@pondkeeper.co.uk.