Clear Koi Ponds: Murky Water & Clear Ponds

Page Summary:  What makes a koi or goldfish pond murky? Contrary to popular belief it is not normally caused by water circulating and stirring up the debris that might be on the bottom of the pond (or at least in the vast majority of cases). Murkiness in fish pond water is almost invariably caused by the suspension of tiny algae cells which rise to the water surface in order to collect sunlight which is the lifeblood of algae. Suspended algae need sunlight exposure to thrive. The more sunlight and the more nutrients for the algae then the more will be the water cloudiness. The permanent solution to this kind of cloudy water is to use an Ultra Violet Clarifier or Viresco. 


The quest for a clear koi pond

While koi fish aren't going to complain if they are kept in a green, murky or muddy pond, you won't have the benefit of watching them while they swim and jump in the water. And that is half the pleasure of keeping koi. Even though goldfish can't compete in terms of spectacular colours and pattern, even they look more attractive in crystal clear pond water.

Apart from making it easier to view your fish, clear water also looks cleaner. A green, algae-infested pond looks unhealthy, even if it isn't. It's rather like comparing a beautifully manicured and clipped garden to one that has been left to grow completely wild. Most people will prefer the effects of the former.

The main reasons for water losing its clarity are:

  • algae blooming in the pond water,
  • silt and soil being stirred up from the bottom of the pond, and
  • inadequate filtration.

Algae is the most common reason that water goes green. It doesn't matter whether the water is in a fish pond, in your swimming pool or spa, or in a bucket left in the sun; if you don't keep the container clean, algae will eventually start to form.

A single-celled plant, alga is most likely to form in hot, sunny water that contains nutrients. Because surface water heats more quickly that deeper water, the shallower the container, the quicker the algae will form.

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While we traditionally treat our swimming pool water with chemicals to keep it clear, clean and healthy, we try to use different methods to keep our pond water clean and clear. One of the simplest is to plant the pond to counteract the conditions algae need to thrive. Quite simply, this involves getting rid of the light and nutrients in and around the pond water. Planting both in and around koi ponds is an ideal way to do this. Marginal plants can help to shade the surface of the water, as can water lilies and floating plants like pond lilies and water fringe. Submerged plants, including some popular oxygenators, will add some shade, but will also compete for space with algae.

A UVC (or ultra-violet clarifier) is a reasonably failsafe mechanism that may be used to get rid of algae growth. Pump-fed and installed with an external filter, these modern-day devices use UV bulbs to get rid of algae. They are safe, literally burning the algae and forcing the microscopic cells to stick together so that the dead algae can be easily removed. The irony though is that a UVC will clear the water so beautifully, the clarity itself can encourage more algae to proliferate. For instance, what often happens is that a UVC will kill all the water floating in the pond, and within a few days, blanket weed takes over, covering the surface.

Of course fish love to eat algae (particularly blanket weed), but they don't always manage to outpace its growth. For this reason some pond owners find themselves forced to resort to chemicals. These include:

  • algaecides that are designed to kill algae,
  • algae inhibitors that are formulated to control rather than kill the plant growth, and
  • chemicals that remove nutrients, primarily phosphates and nitrates.

If algaecides are used, you are likely to end up with a load of dead algae floating in the water. This must be removed or filtrated to get rid of it. A danger is that the decomposing algae will reduce the dissolved oxygen in the water, which can easily stress koi fish.

Soil and silt

Koi are a primary culprit when it comes to stirring up the silt and soil on the bottom of any pond. They are incredibly inquisitive creatures, and they love to go in search of tasty treats that have sunk into the aquatic gravel and soil. Goldfish are smaller and so their pond-bottom activities have less of an impact.

Generally stirred-up soil and silt will eventually settle and the water will clear. If it becomes a frequently recurring problem, you might want to remove some of the silt from the base of the pond. This may be done manually – if the pond is not too deep – or by using a pump that can handle solids. Alternatively you may need to do a makeover that involves draining the pond and cleaning it. On the downside, this will mean you will need to re-establish the pond and get it back into natural balance.

Inadequate filtration

We use filters in koi and goldfish ponds to remove unwanted solid material and to get rid of debris. A biological filter will use the bacteria that form in it to break down toxic waste and harmful organisms.

A filter that becomes blocked because of a lack of maintenance, or one that is not able to deal with whatever needs to be filtered out of the water, needs to either be repaired or replaced. Cleaning a koi pond filter isn't difficult, but you will need to be careful not to damage the parts or disturb the bacteria (presuming of course you have opted for a bio-filter). Making the time and effort to do it properly will only benefit your fishy friends, whether they are koi, goldfish or some either type of pond fish.


Dont stress over pond pH and Testing Koi Pond pH

Interpet Koi Pond Test Kit

I will make a few very important points here which should be taken very seriously by anyone contemplating measuring pH in a koi pond and then TAKING ACTION based upon the measured result from testing the koi ponds water. If you test do it reliably... Interpet lead this pond water testing field of the koi keeping hobby

  1. pH of koi pond water will vary depending on time of day measurement is taken and especially if plants are in the pond. This means if you take a pH at 9am it will not be the same as a pH taken at 6pm. This single piece of information therefore must never be the information relied upon to make fundamental decisions
  2. pH is notoriously difficult to measure even in a laboratory with sophisticated instruments let alone in a koipond or fish pond using a piece of litmus type paper or a vial with coloured scales on it.
  3. If you must measure pond pH and this is a great part of the hobby then take the pond pH at the same time every day and plot the result on a graph. So now what youre looking for is not a single pondwater result but rather a pH trend in the pond water that you can use to sensibly consider a pH strategy.
  4. Very high pH in a koi pond is a serious threat to the well being of koi when levels reach about 9.5 because at this pH level ammonia which is a natural metabolic product of the koi and its existence becomes extremely poisonous
  5. It would be extremely rare for a koi pond to reach dangerous pH levels but could well occur in koi ponds with serious algae problems

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