Guide to Cleaning Fish Ponds without Draining Water (updated 2020)
Fully draining pond water should always be a last resort, and it’s certainly not something you need to do if you want to clean your pond. As a matter of fact, draining your water can actually make the pond dirtier in future as the natural eco-system will be disrupted, especially in wildlife ponds. Even though heavily draining water may be required under some circumstances, in terms of general cleaning, it is rarely a necessity so long as you have the right equipment at hand.
Do I need to drain my pond water to clean efficiently?
A common misconception among some pond owners is that “dirty” water needs to be drained before ponds can be properly cleaned. In-fact, the opposite is often true, with water that appears dirty actually being very healthy and working with the pond’s eco-system to provide a natural cleaning service. Pond water is filled with micro-organisms and millions of beneficial bacteria which are constantly at work to break down harmful substances, such as ammonia and nitrites. These are essential to ponds with fish, and form the basis of the “nitrogen cycle“, which helps keep the pond in balance.
Removing pond water means you’ll also be reducing the natural beneficial bacteria populations, which will cause a reduction in your ponds biological filtration process. Topping up with more water after draining can cause even more disruption, as mains water is usually high in chlorine, which is toxic to much of the natural micro-organisms living in ponds.
Cleaning a pond without draining will ensure that your natural bacteria populations are maintained, allowing them to continue providing bio-filtration after the worst of the waste is removed. If waste levels get too high, you will just need to manually remove enough waste so bacteria can get back to work again – no total drainage required!
Should I perform a water change when I clean?
Water changes (removing and adding water) may be beneficial in some circumstances, but we never recommend a full pond water change (full drainage) as you’ll be effectively resetting the nitrogen cycle. If you have a heavy fish stocked pond it can be difficult to maintain water quality as fish produce so much waste, especially in summer when their metabolisms are high. In cases such as this, performing a small water change during cleaning can help keep ammonia levels down and improve overall water quality. Beneficial bacteria can only do so much and can easily be overloaded in ponds with massive amounts of waste build-up, so water changes can sometimes be a good option for maintaining water condition.
For ponds without fish, water changes should not be required unless your water quality is particularly poor; which you can determine using a water testing kit. For general cleaning, which includes bottom muck, algae, and floating debris, you should not need to remove any water to get the job done. If your pond water testing shows positive results, removing water may cause a drop in water quality and make it more difficult to maintain cleaner water in future.
If you do decide you want to perform a water change, however, you should make sure water is safely dechlorinated before adding to the pond or you could have problems later down the road.
When is the best time to clean a fish pond?
Although cleaning can be carried out whenever you need to, the best times for fish ponds would be at the start of spring and the end of autumn. Cleaning at the end of autumn ensures waste levels are minimal moving into winter so fish have a more comfortable (and safe) topor/hibernation period. Leaving sludge and debris in ponds over time can cause all sorts of problems for fish, especially if water freezes over and no gas exchange can take place. In instances such as this, harmful substances will slowly rise and oxygen content will be reduced, eventually leading to fish becoming sick or dying come spring. Performing a deep clean at the end of autumn is common practice for fish keepers, and should be something you consider if you have koi or goldfish.
Likewise, a small clean can be carried out during spring when temperatures begin to rise and fish become more active. Although it won’t be as large a clean as your autumn one, it is useful to supplement the pond with beneficial bacteria and remove any lingering debris for the best kick-start to the year. Other times when you may need to clean your pond would be to remove algae overgrowth, fallen leaves, or excess plants, such as duckweed.
How to Clean a Pond Without Draining it of Water (Best Methods)
Step 1) Skim the Surface for Floating Debris
First thing to clean in a pond is any floating surface debris, as this will eventually sink and contribute to sludge at the bottom of the pond floor. Removing as much floating debris as possible is always better before cleaning the pond liner or you’ll just be cleaning it again later as it sinks. Floating debris includes things like leaves, sticks, twigs, and dead insects or larvae. These can be removed manually using a basic pond net, or you can make use of an automatic skimmer system for constant clean-up.
If you’re going for a pond net, make sure to pick one up with a wide basket opening and a fine mesh so you can catch all sizes of debris easily. Pond skimmers are a good long term solution if you’re constantly fighting back debris that falls into your pond, or if you have lots of fish and want maximum water clarity. Box skimmers will work to clean the water surface quickly and have a high capacity for larger ponds, whereas smaller ponds can benefit from floating or submerged skimmers due to their lower purchase cost.
Unlike nets, skimmers are better long term investments as they can remove much finer debris which isn’t always easy to see and are also able to work 24/7 to keep the surface clean. If you have a small pond, however, and don’t mind keeping on top of daily cleaning, a pond net should be more than enough!
Step 2) Clean the Pond Floor with a Vacuum
Next step is to combat any bottom sludge you have, and although you don’t need to remove it all, it can be beneficial to reduce most of it before winter so your fish have a safer hibernation period. This is often the step where you may feel draining the pond would help, but this is only necessary if you’re manually removing sludge with a net or rake. Another way to remove bottom muck, which is also much faster and easier, is to invest in a quality water vacuum.
Pond vacuums will allow you to clean the bottom of your pond liner without having to drain water, and the best models will have a variety of different head attachments for cleaning hard-to-reach areas of the pond. If you have a particularly deep pond, you’d want to look for a model which can keep suction at good depths and which has an extendible handle for easier cleaning. Basic models will lose suction the deeper you go, and although they may be ideal for smaller ponds, they may not be up to the job of cleaning the deepest points of larger ponds.
On top of this, you’ll want to have a vacuum with a reliable discharge system for constant cleaning and to make it easier to remove waste. The two vacuum models we recommend are the Oase PondoVac 4 and the Matala Power Cyclone, as they include all these features and will work for both small and very large pond builds.
Step 3) Supplement with Beneficial Bacteria
After cleaning out most of the bottom sludge, you can then supplement with a natural beneficial bacteria product to help break down any lingering waste. Most sludge remover treatments work using highly concentrated bacteria which is able to break down organic matter throughout the pond. Just like a ponds natural beneficial bacteria, sludge remover bacteria works in the same way and can help give the natural populations a boost after a deep clean.
If you have a wildlife pond and want to keep most of your sludge, you can instead just add extra beneficial bacteria to complement the nitrogen cycle. Sludge can be beneficial to wildlife ponds as it provides nutrients for plants, as well as food for insects and micro-organisms. Problems with excess sludge occur mainly with fish as a by-product of its natural decomposition is ammonia, which is highly toxic to koi and goldfish. Without any fish in the pond, adding more beneficial bacteria is a cheaper and better way to control sludge in comparison to removing it all with a vacuum.
For more information on the top sludge remover bacteria and how to use them, check our main article on this here.
Step 4) Control & Remove Growing Algae
Even though algae isn’t technically waste, it should still be controlled and cleaned out so it doesn’t cause issues with water quality and sludge build up. Small amounts of algae in ponds are actually beneficial, providing hiding spots from predators and making good snacks for goldfish. Problems with algae occur when it’s left to grow uncontrolled and rapidly takes over the pond system. Algae blooms will cause issues with sludge as old plants die and sink to the bottom, with this gradually reducing oxygen content as bacteria work to break down the new waste.
You don’t have to drain a pond to combat algae, and even string algae attached to the pond floor can be removed with the right mix of treatments. To combat free-swimming algae we recommend installing a UV clarifier which will filter water and destroy algae at the cellular level. For removing deeper string algae that won’t fit through a clarifier, using a pond vacuum will make short work of the nuisance plants.
Algae can also be controlled in the long run by adding more plants to your pond, as they directly compete with algae for nutrients, gradually slowing it’s growth. For fast control of algae, however, a combination of a UV clarifier and a vacuum should be enough to remove almost all of the plants without the need to drain any water.
Step 5) Clean & Optimize Water Filtration
A final thing to do when cleaning a pond is to ensure your water filtration is the best it can be to reduce future cleaning and maintenance. A pond with a healthy biological filtration system will have little problems with water quality, and a filter with efficient mechanical media will reduce overall debris in the pond. Although filters should be rarely cleaned as it can harm bacteria living in the box, it’s sometimes necessary if the media has become completely clogged. Likewise, mechanical media can become damaged over time and may need replacing every few years to ensure optimum filtration is taking place.
Having an efficient filtration process in place will help reduce overall cleaning and also improve water quality for pond fish. For further information on optimizing water filtration, cleaning, and what equipment to use, see our articles below: