Does a Fish Pond Need Plants? (Benefits & Drawbacks)
A pond doesn’t need to have plants to be healthy, and most can do fine with little or no natural foliage so long as the pond is well cared for. With that said, pond plants come with a whole range of benefits, so you may want to consider adding them anyway. For starters, plants provide water filtration, better clarity, algae control, more oxygen, and even shelter from predators! They also look fantastic when they mature and can turn even the most barren of ponds into aesthetic water gardens.
Ponds without plants that have fish will require regular water changes to ensure nitrate levels do not become too high, as there will be no plants present to make use of this compound. If nitrates are left unchecked algae will bloom and you may have a crash in pH, which can harm koi and goldfish. Nitrates are produced at the end of the nitrogen cycle, where beneficial bacteria break down ammonia (from waste) into nitrites, and then into nitrates. Since nitrates have no where to go, they either need need to be removed via plants, algae, or regular water changes. Testing water regularly is good practice for all fish keepers, which can be carried out with pond test kits. If your nitrates are high, you may want to consider a water change or some plants!
Even though pond plants have their benefits, they also have some downsides, too, and may not be suitable for all pond owners. The choice of whether to add plants would depend on your type of pond, whether you have fish, and what benefits you want from the plants to help solve any specific problems. Plants usually take a long time to show their true potential, so they’re not always the best choice for short-term problems, but can certainly shine if given the proper care and attention.
Do I need a filter box if I have plants?
A major advantage of having a heavily planted pond is that plants provide natural filtration, helping remove excess nutrients, sludge, and nitrates. A pond without mechanical filtration is called a “natural” or “wildlife” pond, and the filtration process is carried out largely by the plants themselves. This form of water filtration is effective for these type of ponds as they’re not likely to have any fish, so the overall bio-load (waste) is much less in comparison to a fish pond.
If you intend to have fish in your pond, including goldfish or koi, we strongly recommend adding a filter box even if your pond is heavily planted. Fish, especially koi, are very sensitive to changes in water quality, and much prefer water to be stable and within a specific range of values. Fish also produce A LOT of waste, and plants likely won’t be able to remove enough to keep harmful substances in check. Even with a healthy beneficial bacteria population, there may just be too much regular waste to remove without a filter box to help.
Will fish eat the pond plants?
Both goldfish and koi can eat most pond plants and algae, but are less likely to take bites from a plant if they’re well fed on a regular basis. You’ll notice koi eating more plants and string algae than goldfish as they’re bigger and have more options for food. They particularly love the roots of plants, and enjoy striping the roots of any algae and occasionally eating them whole. This can be a problem if you’re trying to grow new plants which have yet to become established, but is likely not a problem for older plants with vast root systems. Most plants can still survive with some leaves and roots taken, but only if the plant is already healthy and established in your pond.
Submerged plants, such as hornwort, may be good choices if fish keep eating other plants as they’re considered more “fish proof”. They also provide great water oxygenation and underwater shelters when they become established, making them ideal for hiding and even breeding.
Feeding koi regularly will help stop them eating too many plants and roots, but you may still need to section new plants off from fish until they start to grow. You should also always make sure to add new plants to sturdy water baskets, which can be purchased for both floating and marginal varieties, as these will help stop fish eating both roots and plants all at once!
How do I know which plants are best?
Choosing the best plants would depend on what your want to achieve in your pond, as some provide better oxygenation and others better shade/shelter. For example, submerged plants are the only type which can oxygenate the water as all others will respire oxygen directly into the air, so you would need to choose a underwater variety if you want extra oxygenation. Sometimes the choice of best plant is also entirely down to personal taste, and the choice would depend on it’s looks, color, and even how it flowers.
For a more in-depth guide on choosing the best plants and some of our personal recommendations, check our full guide on the best plants here!
Benefits of Adding Pond Plants:
1) Plants provide natural water filtration
Firstly, pond plants provide natural filtration to your water, helping remove excess nutrients, such as nitrates and phosphates, and using these to grow. Excess nutrients in the water come from organic waste buildup (i.e., sludge), and plants love that stuff as natural fertiliser! The same thing occurs with fish waste – ammonia that is released is broken down by bacteria into nitrites, and then into nitrates, which plants are able remove from the water, naturally filtering it. Without plants nitrates have nowhere to go, so the only way to remove it is with water changes.
Excess nutrients in the water can cause all sorts of problems, ranging from nuisance algae bloom to changes in water clarity, so having extra forms of filtration alongside your normal filter box is always a good thing. If you have fish, plants are especially helpful during summer when fish start producing more waste due to their increased metabolisms. Beneficial bacteria may not be able to keep up with the bio-load, so plants provide a helping hand removing excess nutrients and sludge from the pond.
This extra filtration will also help with water clarity, contributing to clearer and healthier pond water. Excess nutrients and substances can cause water to become murky, so having less floating particles will make water much more clear in the long run.
2) Plants help oxygenate the water
A second major benefit is that some types of plants, known as submerged plants, are a great way to help oxygenate your pond water for fish. During photosynthesis, these plants release oxygen directly into the pond water and remove harmful carbon dioxide and excess nutrients. If you have a heavy stocked fish pond, you’ll need plenty of dissolved oxygen in your water for your fish to remain healthy, and this can be difficult during times of naturally lower levels, such as summer. Submerged plants are a good way to add additional oxygen naturally, and during summer they’re at full growing strength and production, which is exactly when fish need it most.
This extra oxygen will also help your biological filtration become more efficient, as beneficial bacteria require oxygen to break down waste and harmful substances. The more oxygen you can provide during times of high waste, the more waste matter your bacteria can help neutralize.
3) Plants provide shelter to fish
Floating plants and submerged plants act as natural fish shelters, allowing fish to hide from predators and relax away from harsh UV light. Floating species, such as water lilies, grow large foliage alongside their flowers which fish can hide under when needed. Submerged plants, such as hornwort, create dense underwater forests which provide both shelter and oxygen to pond fish.
If a predator is hunting around a non-planted pond and a heavily planted pond, there is a much higher chance fish will be taken in the non-planted pond as there is no natural shelter for the fish to escape to. Herons, hawks, cats, and raccoons can all be deterred from eating fish if the pond is planted enough to provide shelter and natural camouflage.
4) Plants help shade your pond
Another benefit is that floating plants and marginal plants both can provide partial shade to pond water from strong UV light. This additional shade helps slow down nuisance algae growth, and also helps bring down the overall water temperature, making it more comfortable for goldfish and koi. Fish will also enjoy the areas of extra shade, and you’ll often see them relaxing there during the hottest days to get away from the sun and heat.
5) Plants help control nuisance algae
Pond plants will compete with nuisance algae for nutrients and sunlight, as they both require the same ingredients for growth and photosynthesis. Plants will remove nutrients from the water as they grow and help shade water from sunlight, which will help slow down the growth of algae. Nitrates can also only be removed with plants or regular water changes, and if left unchecked algae will quickly make use of it to bloom. Pond plants will help remove excess nitrates and work great in heavy stocked fish ponds so you can reduce the number of water changes required.
Drawbacks of pond plants:
1) Plants will require extra maintenance
Although not a huge amount of work, plants will still require some extra maintenance to stay healthy. Some plants will require more work than others, such as marginal plants, so picking certain types may be best if you want minimal involvement. Submerged plants are the easiest to care for and some don’t even need to be planted in substrate as they will feed their roots directly into the bottom sludge. Floating plants, such as water lilies, will require planting in a water basket around a certain depth to grow healthy. Marginal plants will also require substrate and a specific depth, and will also need to be trimmed back every now and again so they don’t overgrow. More information on different plants and planting tips can be found in our guide here.
2) Plants will contribute to sludge/waste levels
Regularly trimming plants and removing any dying foliage is important so that it doesn’t contribute to sludge levels in your pond. In particular, after pond plants bloom they will leave a lot of pollen and flower heads in your water which should be skimmed off the surface before it sinks. Leaves will also start to die eventually as new ones grow, so these can be snipped off before they can sink.
3) Plants will take a LONG time to provide most benefits
Most the the benefits mentioned above are long term, and you won’t see the maximum results from a planted pond for months or even years. For example, submerged plants can provide oxygen and filtration almost immediately, but it may take months before there is enough growth to make any visible difference in water quality. It will also take time for plants to grow enough to provide shelter and shade, as both things require plenty of foliage to be effective. Algae will also have more of a foothold over plants to begin with, and you may need to treat any algae problems before adding new plants or the algae will slowly starve them of nutrients.
If you have immediate problems with oxygen, algae bloom, or predators, pond plants likely aren’t the best short term solution. More direct methods may be needed to solve the problem, but pond plants can be added alongside and will be able to provide similar benefits overtime as they become more established in your pond.