How to get really clear pond water
The ultimate aim for any fish pond owner is to be able to view and enjoy their fish. Here’s the Swell UK guide to getting gin-clear pond water that you can see through right down to the pond liner.
Fit a UV Clarifier to clear green water
Ultra Violet Clarifiers are purpose-built to destroy the unicellular algae that cause green water in ponds. You cannot overdo the amount of UV you have on a backyard pond or water gardens but you can underdo it, and have too high a flowrate for it to be effective.
So choose a large UVC model and make sure that your pond pump is pumping under the maximum flow rate for that size of UV. Run it 24 hours per day, change the bulb every 6-12 months depending on make and model, and keep the quartz sleeve clean too for maximum ultraviolet light penetration.
Still not sure which UVC you need for algae control? Select a pond filter with UVC built-in.
Trap the waste, flush the waste
You need really effective mechanical filtration if you want clear pond water which is free of particles. Use a large pond filter or several filters in combination and ensure that they have a sponge, static plastic media or a drum filter to capture those waste particles as they flow into the filter.
The best mechanical filters are ones which are self-cleaning and can even automatically clean themselves, sending the dirt down the drain on a regular cycle. Remove the waste before it’s broken down, and you’ll have less nitrate and phosphate build-up, and less algae too.
A pond skimmer can also be used as type of mechanical prefilter, again trapping waste before its broken down.
Add some carbon
Activated carbon is a chemical filter media which soaks up dyes and discolouration from the pond water. Over time the water will turn yellow from biological processes, fish food, fish waste, leaves and dead algae, so add some activated carbon to your filter and it should return your clarity to that of tap water. Place it into a net bag first though so it doesn't escape from the filter and flow back into the pond.
Use a pint glass to analyse how clear your water is, by holding it up in the light.
Add some beneficial bacteria
Bacteria are clever little things and have a solution for most fish-related problems. Add some beneficial bacteria aimed at clearing water and it should do exactly that, seeding the water with bacteria and enzymes which get to work reducing waste and polishing the water. Get it right and the use of beneficial bacteria can clear pond water naturally. Biological filter media is designed to give nitrifying bacteria a new home.
Change the pond water
Water changes have a myriad of benefits including lowering nitrates and phosphates, diluting hormones and helping to buffer pH and KH. Set a regular routine of water changes using water conditioner or a de-chlorinator, or better still set up a mains tapwater feed with a ball cock and a drain, to permanently trickle fresh water into the pond. A constant trickle of fresh, new water is best for growing fish to the maximum potential too. Use a pond pump and hose to change water quickly and easily.
Use a flocculant
Flocculants are liquid treatments that are poured into the pond to clear the water. They actually work by clumping particles of debris together, forming larger particles which then either fall to the bottom of still ponds, or are removed by filtration. They clear water best in conjunction with mechanical filtration, and they actually make the pond water clarity look worse for a few hours before it gets better. But a dose of flocculant every now and then can really polish garden pond water and help to make it look gin-clear.
Shade the pond
Few sunlit ponds enjoy clear water year-round as its too tempting a breeding ground for nuisance algae. If designing a pond place it in partial shade, build a pergola or fit a sail over the pond to protect it from the full glare of the sun’s rays. Aquatic plants can be used to shade pond water too and up to two thirds of the pond surface area can be covered with pond plants.
Introduce some pond life to clear pond water naturally
If its an unfiltered wildlife pond, Mother Nature has its own army of water clarity devices. Water Fleas, also known as Daphnia, are tiny aquatic invertebrates that filter feed on microscopic algae in the water, clearing it as they feed.
Add a bag of live Daphnia and if it is an otherwise healthy pond they will multiply rapidly. They are capable of naturally clearing pond water within weeks. Water Fleas are eaten by pond fish however and get sucked into pumps and filters, so are only recommended for still, fishless garden ponds, with no pond filters.