13 common mistakes when building and maintaining a garden pond

fish pond mistakes

There are a lot of people who would love to build a pond in their garden but many fail because they make some basic mistakes.

In this article we are going to go through the 13 most common mistakes that people make when building their garden pond and maintaining it after its built.

1. Choosing the wrong location for a garden pond.

Just because you have a bit of ground in your garden thats unused it doesn’t mean it’s the perfect place to build a pond.

Getting the location right is very important and that unused area is probably unused for a reason, maybe its out of the way and isn’t seen from most parts of the garden, why would you want to build a garden pond that you can’t see.

A low area of a garden is not the best place to build a pond as rainwater will run into your pond along with all the pollutants it can bring and can quickly overflow a pond, in extreme cases the the extra amount of water can lift a pond liner.

Positioning a pond under a tree is another no no, the tree can cast too much shade on the pond, drop leaves into the water and the tree roots could damage a pond.

A pond likes to have about five hours of sun a day but also needs some shade, putting it in a shady area that gets no sun and it will soon become stagnant, however you can get away with a pond that sits in dappled shade or is in full shade for just part of the day.

Avoid drains, underground pipes and cables. Hopefully you will have the perfect location in your garden that not only avoids the pitfalls above but fits in with your garden design.

2. Not realising how much work goes into building a pond.

There are so many people who think its just a case of digging a hole in the garden, putting in a liner of some sort and the job is done.

Unfortunately it’s not as simple as that, it’s going to take a lot of hard work starting with laying out the pond size and digging.

Digging is hard work, have you ever dug a hole for a plant or for a fence post, now imagine how big and deep a pond is and you can understand how hard it could be.

The type of soil you have and how many stones are buried in the ground can play a huge part on how difficult it will be.

Excavating the amount of soil needed to make a good sized pond should not be underestimated.

3. Building a pond that’s too small.

This is one of the mistakes you want to avoid if the pond is going to be stocked with fish, it sounds easier, less digging and easier to construct, but there’s nothing worse than trying to make a small pond bigger if you get this stage wrong.

Many pond builders think a small pond is going to be easier to maintain, in fact it’s the opposite, a larger pond is a lot easier to maintain as long as you build it right in the first place.

A bigger pond will give enough room for fish and plants to grow and thrive, a smaller pond will soon become overcrowded and less stable, so build the biggest pond you can.

4. Building a pond that isn’t deep enough.

Building a pond that isn’t deep enough is going to be a problem if you want to keep fish, if your pond is just a water feature you can get away with shallow pond.

Fish need enough water to be able to swim and thrive, but they also need to have a deep area of water to survive the winter months and to protect themselves from predators.

Shallow water can become too hot in the summer which fish don’t like and the water can quickly evaporate from a pond, so a deep area of water is a must, about a third of the overhaul size of a pond should be adequate.

If Koi fish are being kept the deepest part of a pond should be about 1200cm, for common goldfish it should be 600cm deep.

5. Not having ledges in a pond.

This is another common mistake that new pond builders do, They dig out a bowl shape with gently slopping sides that get deeper and deeper towards the middle of the pond.

Pond ledges are a necessary component of a pond, they are used for placing rocks on to hide the pond liner which is often left on show when constructing a pond, there’s nothing worse than seeing a pond liner sticking out of the water.

If the pond has been built with sloping walls any rocks that are placed to hide the liner could slide down and end up in the middle of the pond.

Pond ledges are also used for placing semi-aquatic plants that have their roots submerged in the water while the rest of the plant is above water, so without ledges you wont be able to place these plants.

6. Choosing the wrong rocks and stone for the pond.

To make your pond look natural you should use rocks, stone or boulders in various sizes, these stones will also hide the liner along with gravel.

All too often when building a pond the choice of rocks is an after thought when it should be designed into the pond from the beginning.

Getting the right balance of large and small stones is essential to give a pond the desired naturalistic appearance, unfortunately some pond builders only use small stones because they are easier to manage but doing this falls short of the desired aesthetics, you need to have large rocks to balance the stonework out.

There are people who leave out the stonework altogether, I’m not saying it’s a bad thing to do, but for the aesthetics of the pond I don’t think it looks that good.

Another reason for using rocks and stone along with gravel is it also functions as a habitat for a variety of benthic organisms, from bacteria to crustaceans which all play a part in the success of a pond.

7. Not using adequate filtration if there are fish a pond.

Unlike real ponds, rivers and streams that have a natural water source flowing through them a garden pond is a closed body of water that has no fresh water to keep them clean.

Do you need a filter system in a pond? No, if the pond has no fish or is a wildlife pond with a high level of plants and just a few fish you could get away without needing a filter, just let nature do its thing.

If you want to keep a good stock of fish in a pond you will need a filtration system, the more fish you have and the bigger the pond you have the bigger the filtration needs to be.

One of the biggest mistakes is using a filtration system that in theory should be ok but as the fish grow and multiply more waste is produced and it gets to a stage when your filter can’t cope anymore, so always go with a larger filtration system than you think you will need.

You should also use two types of filter, a mechanical one to remove the waste products that lead to extreme algae growth and a biological one to keep your pond free from ammonia and toxins.

8. Not leaving enough time for a pond to adjust.

A ponds eco system, especially a new pond needs time to adjust before you can start adding fish.

A big mistake for a new pond is adding fish as soon as the pond has been completed. You need to get the chemical balance in the pond right before you can even think about adding fish if you want them to survive.

Filling a pond with tap water which contains chlorine and chlormines is harmful to fish so it needs a suitable water conditioner/dechlorinator.

The filter needs to be up and running to establish a good bacteria colony, this can take between 2 and 4 weeks, although you can add a treatment which will speed up the process.

Leave at least 4 weeks before adding fish and check the water quality with a water tester before doing so.

Adding too many fish at one time can upset the balance, so add them gradually 1 or 2 at a time over many weeks if not months checking the quality of the water as you go, only adding more once the chemical levels are right.

9. Overstocking a pond with fish.

Many new pond owners have the tendency to add too many fish into a pond which is a big mistake.

Fish need oxygen to survive, but too many fish will deplete the available oxygen in the water which is dangerous for the fish.

Fish produce waste (poo) which creates harmful chemicals in a pond, the more fish you have the more waste is produced, more waste equals more harmful chemicals, it’s like a vicious circle, so keep fish to a manageable amount that the pond can cope with.

10. Overfeeding fish.

As a new pond owner many people overfeed their fish because they think their fish are hungry.

When fish are overfeed they produce a lot more waste, more waste equals more chemicals, fish only need to be feed once a day and only feed them what they can eat in about 3-5 minutes, just sprinkle food on the water a bit at a time and when they stop eating stop feeding.

No matter how hard you try to keep algae out of a pond it’s still going to make it’s way back, overfeeding fish is a sure way a pond will develop algae bloom.

If food is not eaten, take it out with a net or it will fall to the bottom of the pond and rot and use less food the next time the fish are feed.

Overfeeding fish is not going to kill them, they may get fat but it’s the waste they produce that’s the problem, plus further down the line they may have liver or other internal problems due to being over fed.

Fish will often come to the surface of the pond and interact with you when you go near them, don’t think they are hungry and feed them if the’ve already been fed.

11. Leaves and debris in a pond.

Not removing leaves and debris from a garden pond can bring big problems further down the line.

Decaying material will produce ammonia and as we know this is bad for fish, so removing debris as soon as possible will reduce the amount of waste which in turn is good for water quality.

You can also reduce the amount of algae growth by fishing out debris from a pond before it starts to decay, just have a good net handy to help get rid of the debris.

12. Adding new water to an established pond.

Once a pond has reached a good balance and has an established biological filter system it can be dangerous to add new water.

Adding new water into a seasoned pond can introduce toxins and pollutants into the system, disrupting the entire biological filtration which has built up over time and could shock the ecosystem.

The only reason an established pond would need a water change is if there was a high level of harmful chemicals in the water that couldn’t be controlled naturally or with the use of filters.

If a water change is needed do a partial change to minimise the effect on the pond.

If tap water is used use a chlorine remover to remove the harmful chemicals.

The best way to do a water change is a little bit at time so the water that’s going into the pond is dilluted with the pond water.

13. Not having enough shade on a pond.

Although I said a pond needs sunlight it also needs to have some form of shade to slow down the algae growth which is caused by temperature change due to too much sunlight..

You want to aim for about 1/2 – 1/3 of the surface of the water to be shaded, this can be done with plants that float on the water such as water lilies or plants and bushes around the edge of the pond. x