How to Keep Leaves out of a Fish Pond for Better Water Quality in Autumn
The single best way to keep leaves away from your pond is to stop them entering in the first place! Installing a fine mesh pond netting is the easiest way to catch leaves and prevent them building up on the pond floor. The netting will take care of leaf collection, and you’ll just need to sweep down the leaves every week or so to stop them decomposing on the mesh and leaking through.
Many pond owners choose not to install netting as it can be an eyesore, and this is true for some lower quality brands. If you invest in a high quality pond netting, however, they can be almost invisible against the pond water and will still be strong enough to catch a large amount of debris. Pond netting that is black is ideal if you want to minimize it’s visibility, and you can even opt for a floating style netting which hides on top of the surface water.
In terms of catching leaves, supported netting is usually better as the leaves won’t be touching the water and won’t be able to start decaying and leaking tannin (color). It’s more visible in comparison to floating netting, but it’s easier to clean and also offers better protection from predators, such as herons. Even if you don’t like the ideal of pond netting, you can simply install it at the start of autumn to make your pond easier to manage and then remove it come winter after most of the leaves have fallen. Unless you don’t mind manually removing leaves and cleaning bottom muck, we recommend most pond owners install a quality netting to make autumn and winter more manageable and to reduce the chance of problems.
If you don’t like the idea of netting, an alternative is to install a pond skimmer which collects debris right off the surface water. You don’t need a large pond to benefit from a skimmer either, as they come in a variety of styles, including small floating skimmers, medium surface skimmers, and large box skimmers.
Box skimmers are the most common type and are very similar to what you see in swimming pools, often built into a side of the pool itself. These are installed along the margins of a pond, below the water line, and work alongside the natural water current to “skim” the water and collect any floating debris. They contain a fine mesh basket inside which then needs to be emptied every week or two as the skimmer fills up. These type of skimmers are ideal for larger ponds, as they have a large debris holding capacity and require good water flow to function efficiently. They’ll also need to be installed manually and fitted along the pond liner, which can be difficult if you’re not experienced with pond equipment.
An easier option for medium to small sized ponds is to install a floating skimmer or submerged skimmer (pictured). As the name suggests, a floating skimmer literally floats around the pond and collects debris as it goes, and a submerged skimmer sits on a shallow pond shelf and skims against the water current. The benefit of both of these skimmers is they’re easier to install, cheaper to purchase, and work very well for smaller ponds which get a few floating leaves in autumn. The downside is they’ll need to be cleaned more regularly as their capacity is lower, but it’s still better than having debris decompose and cause problems for fish in winter! They also help aerate the pond by creating water flow, and some even oxygenate with built-in air pumps – bonus!
If pond netting and skimmers are out of the question, or if a few leaves are still getting through your netting, you can use a regular pond net to manually collect the floating debris. Although not the easiest method to control leaves in your pond, it gives you the most manual control over cleaning and would suit smaller ponds where skimmers may be overkill. Most pond nets would do the job, although we recommend a net with an adjustable length, strong handle, and wide basket with fine mesh for best results. Depending on how many leaves you get in your pond, you may need to perform daily cleans to stop them from sinking, but this shouldn’t be a huge problem so long as your pond is fairly small and easy to access.
This isn’t an ideal method for larger fish ponds, as debris build up in autumn can quickly become a huge cleaning task if there is a lot of water to cover. In these cases, we’d recommend a combination of manual removal and the addition of a regular pond netting cover or skimmer to make life easier.
4) Reduce Debris with a Pond Vacuum & Beneficial Bacteria
If you’ve ready got plenty of decomposing leaves and matter on the pond floor, we recommend cleaning it out before winter arrives so your pond is safer for fish. You can use a regular fish net for this if your pond is small, but you can’t beat the speed and efficiency of a quality pond vacuum for larger ponds!
If you have a heavy stocked koi or goldfish pond, pond vacuums are the best way to keep on top of cleaning duties as they can suction out pretty much all types of matter which can cause issues with water quality. Quality models will have different nozzle attachments for cleaning in difficult areas, as well as a high capacity chamber for maximum operation. Pond vacuums are a good long-term investment, especially for fish keepers who want the best water clarity and an easier year-round cleaning routine.
For even better cleaning results in autumn, you can add a cold weather beneficial bacteria supplement which will help break down any left over waste matter in the pond. Supplementing with more bacteria can help improve biological filtration going into winter, and ensure you have a healthy population come Spring. Beneficial bacteria supplements won’t be able to remove large amounts of muck by themselves, but they are a nice way to complement your autumn clean out and improve water filtration for fish.
5) Test Water Quality & Maximize Filtration
Each of the above steps will help you keep leaves away from your pond as well as clean out decomposing leaves stuck at the bottom. However, there are still things you can do to improve the condition of your pond in autumn which will help with water quality and make maintenance a little easier. These tips won’t be able to physically remove leaves, but they can help reduce problems that are caused by leaves and decomposing matter in general. See below for further ways to improve ponds with heavy leaf build-up and organic waste:
- Ultimate Guide to Winter Fish Care
- Tannin (Brown Color) from Fallen Leaves
- Best Filter Media for Water Quality
- Cleaning & Optimizing Filter Media
- How to Lower Ammonia in Ponds
- How to Test Water Quality
Are Leaves Good for a Garden Pond?
Autumn is certainly one of more spectacular seasons, with plants tucking in for winter, trees dropping their leaves, and everything going from a lush green to a rustic orange as the colder weather sets in. It’s a seasonal change that certainly looks great, but it’s not the best one for garden ponds if you don’t prepare yourself for it.
Leaves that fall during autumn need to go somewhere, and chances are many of them will end up floating on your fish pond. They may look pretty floating on the water, but leaves are actually one of the biggest contributors to waste build-up, harmful substance spikes, and winter fish death. The problem isn’t when they’re floating on the surface, but when they become waterlogged and sink to the bottom of your pond. Small amounts won’t have much of an impact, but a large amount of freshly decaying matter in a small amount of time will hugely increases the bio-load of a pond, especially one with fish.
If you have goldfish and koi and plenty of garden foliage, mainly trees, you owe it to yourself as a fish keeper to ensure your pond is safe through the season for your fish to survive comfortably. This usually means preventing leaves from building up, or cleaning out decaying leaves and bottom waste before winter arrives – a practice that helps to “winterize” a fish pond for the colder season ahead.
Will leaves in a garden pond harm fish?
Small amounts of organic debris and leaves are a natural part of a ponds eco-system, and small amounts won’t have much of a negative impact on the pond. If there are no fish in your pond, leaves are even less of an issue and the choice to remove them would depend on how clear you like your water.
However, if you have goldfish and koi carp in your pond a large amount of decomposing leaves and debris can cause all sorts of problems, especially over winter. Leaves that become waterlogged and sink will slowly decompose on the bottom of the pond floor as beneficial pond bacteria break them down. This matter forms what we call “bottom muck” or “sludge”, which is essentially all the organic waste that accumulates on the pond liner. Bacteria gets to work fast breaking this matter down, reducing harmful by-products, such as ammonias and nitrites, into less harmful nitrates and nutrients for plants.
Major problems occur when the amount of waste matter is too much for your ponds biological filtration (beneficial bacteria), and they cannot work fast enough to keep up with new bio-load. Often this happens during autumn when massive amounts of leaves fall into the pond and sink all at once, causing bacteria to work over time. As bacteria work they also use oxygen to function, which lowers the amount available for fish in the water. If the waste matter is too much and bacteria can’t keep up, oxygen will continue to lower and waste substances, such as ammonia, begin to build which are highly toxic to goldfish and koi.
What about leaves in the pond over winter?
Cleaning out leaves and bottom muck before fish begin hibernating is one aspect of “winterizing” a pond. If you have fish you should perform a full pond clean out of sludge and waste so koi and goldfish have a more comfortable time during winter. Often waste caused by leaves can be prevented before they can sink (i.e. pond netting), but if you don’t have netting or just have small amounts of muck, it’s advised to give your pond floor a good clean in autumn.
The reason for doing this is because during winter everything slows down in a pond, including fish and beneficial bacteria. Fish that are hibernating will be surviving off their summer fatty stores, and their metabolisms, bodily functions, and immune systems will all be slower than in summer. Waste that is left in the pond over winter will slowly ferment all season, causing a gradual build-up of harmful substances, as well as lowering oxygen content. If your pond freezes over and no gas exchange can take place, the problem is even more dangerous to fish!
On top of this, and because oxygen is lower, regular aerobic bacteria cannot break down the waste so slower anaerobic bacteria will take over. This type of bacteria uses carbon dioxide to process waste, but they also produce highly smelly hydrogen sulfide as a by-product. As this builds up over winter, and then spring arrives, it will mix with upper layers of water and cause your pond to smell of rotten eggs and sewage (not nice!).
Reasons to Remove Leaves from Fish Ponds (Summary)
1) Leaves increase bottom muck/sludge
Leaves, just like all organic debris, will contribute to sludge on the bottom of your pond as it becomes water logged and sinks. This isn’t a huge issue for ponds without fish, but it can still cause problems with smelly pond water come spring if oxygen content is low over winter. If you have pond fish, cleaning bottom waste is always recommended before winter to ensure water quality remains good and oxygen is available to koi and goldfish during hibernation.
2) Rotting leaves decrease water quality
All decomposing matter produces waste substances, which beneficial bacteria need to break down so they’re safe for fish – a process called the nitrogen cycle. If the amount of leaves is too much for your biological filtration, you may see spikes in ammonia and nitrites which can be deadly to aquatic life. These increases, whether gradual or sudden, reduce the ponds water quality and can have a lasting effect on koi and goldfish if left untreated.
3) Leaves can cause brown pond water
Although water clarity, or clearness, isn’t always an indicator of poor water quality it can still be a nuisance as decomposing matter can stain water brown. This is caused by tannin (organic color) which leaks from matter being broken down in water, often causing water to turn muddy in color. Leaves are a huge contributor of tannin in ponds, and if you don’t clean out bottom muck during autumn you may notice your pond turn brown when spring arrives and tannin mixes with the upper layers.
4) Leaves can cause fish problems over winter
The most risky time to leave large amounts of debris in a pond is during winter as fish are the most vulnerable and ponds may freeze over. Having debris during spring and summer may cause issues with water quality, but it’s unlikely to seriously harm fish if your water filtration is in good order. During winter, however, most pond equipment is turned off, which means there is less aeration and filtration taking place. On top of this, if a pond freezes over there will be nowhere for harmful gases to escape, which can lead to a dangerous mix of ammonia and carbon dioxide build-up – both of which are deadly to fish in high quantities.
Pond consultant and long-time hobbyist who enjoys writing in his spare time and sharing knowledge with other passionate pond owners.