Clear Fish Pond Water | How To Clear Algae From A Fish Pond & How To Keep A Fish Pond Clear

how to stop your pond from going green ...

I received an email from John who lives in Florida yesterday and I sympathize with his predicament. He is a subscriber to my free pond keeping newsletter ...

He is suffering from an all too common pond related problem... Green water caused by suspended floating algae. He was looking for the proverbial answer to how to keep fish pond water clear!

Even though I have written about how to clear algae from a fish pond on numerous occasions I believe that elaborating on why green pond algae forms is the only way you can learn how to keep a fish pond clear and maintain clear fish pond water.

Here is John's email and then my somewhat longer response. Any pond owner who suffers from this nuisance and wants to know how to clear algae from a fish pond will find this newsletter useful. I also touch upon the other pond nuisance blanketweed and how you can remove this string like algae from your pond easily and permanently.

"Hi Sean

I'm not suffering from "Blanket Weed," but do have an algae problem that is causing my pond water to turn green.

I've got a biological pond filter with a UV light; one that we back wash every three days of so.

I've added some chemicals (pond algaecide) to try to get rid of the suspended algae, but to no avail!

I live in Florida and it is so hot that our koi and other pond fish are not coming up to feed because the water is too warm.

My pond is half covered by floating water lilies and water hyacinths and is about 2.5 feet deep.

What else can I do to get rid of my green pond water or is it a case of the hot weather being just too much to try and control the algae right now?

Is keeping fish pond water clear an impossibility? Any help would be really welcome.

John, Tampa Bay, Florida, USA"

This is my reply to John...

Hi John,

I sympathize with your problem of how to stop your pond from going green ... A clear fish pond, where you can actually see your pond fish and other pond inhabitants is after all the aim of all pond keepers.

Green Water caused by suspended algae is the blight of many a pond owner. Luckily there are solutions however to the all to common problem of "How to clear algae from a fish pond"

Your problem is one of the most common encountered by nearly all garden fish pond keepers and has to be resolved if you're going to get maximum enjoyment from your pond.

It is also easy to resolve if you understand what's happening and then do the "right thing."

It will help if you understand how algae multiplies and why it makes water murky green or brown.

Essentially algae (consider them as tiny plants) is a normal phenomenon in all ponds, lakes, rivers but there is a balance between the growth nutrients available for the algae and the rate of growth and also death of the algae.

The algae never reach levels at which they cloud the water. In other words they are dying as fast as they are multiplying and the water thus remains clear. The algae are still there ... you just can't see them.

If there is a lot of nutrient ("food"), lots of sunlight and warm water then algae will thrive and shift the equilibrium in favor of
the algae growth rate being higher than the death rate.

Since the growing algae population is now outpacing the rate of those dying it is only a matter of time before the water goes cloudy.

The water goes cloudy because algae rises to the water surface where they can gather as much sunlight as possible to aid in their growth rate (photosynthesis) and matters get worse not better.

"Food" or nutrients as far as algae is concerned are essentially nitrates and these are produced by the normal fish metabolic processes.

How To Keep A Fish Pond Clear ... Kill The Algae Or Remove Its Food Source

It follows from what I've said above that if you can kill the algae FASTER than it is growing even if there are high nutrient levels in the water OR if you can remove the nutrient source then the water MUST remain clear because the algae population cannot build up to levels which cloud the water.

Under normal conditions it is difficult to remove the nitrates and as such there is always food on which the algae thrive.

Aquatic pond plants to some extent help in removing nitrates but never reduce the nitrate to zero levels otherwise the plants would die.

The UV light from the UV Clarifier or UV Sterilizer has one single function... TO KILL ALGAE.

The action of a UV light is to kill the algae FASTER than it forms ... it does not eradicate algae!

This is an important point to understand. Algae, suspended in water, is pumped through the UV Clarifier. The living algae is irradiated and killed, thus keeping green water away and maintaining clear fish pond water.

If there is enough power in the UV unit to completely suppress algae growth then the water will remain clear and you have a solution relating to how to clear fish pond water. If however the power or irradiating effect of the UV is insufficient then water will remain cloudy.

If your UV Clarifier is not maintaining clear fish pond water then there are 3 possible reasons...

  1. The lamp has gone beyond its active period (max 8000 hours or approx 1 year running 24/7) after which it MUST be changed. After a period in use the capacity to irradiate is completely lost. Lamps do not always last 8000 hours ... Click here for Replacement UV Lamps...
  2. John, your UV may not have enough power (Watts) for your specific situation. You have very warm water and your pond is probably overstocked with fish. Remember also your fish have grown over the last year and thus produce more nitrate nutrients. This might mean that what worked last year will no longer be sufficient. However without knowing dimensions of your pond or volume and your existing UV wattage I cannot really comment. Suffice to say UV works every time if correctly sized and maintained for prevailing conditions. Send me this information and I can comment further.
  3. If your UV contains a quartz tube (and most do) there is a possibility that it is "fogged up" thereby reducing light transmission. In this case it needs cleaning since this also results in reduced irradiation levels.

Irradiation capacity is expressed as Watts ... thus a UV Clarifier is specified as 8 watts, 15 Watts and so on. If I have to guess I would say your UV is undersized for the prevailing pond conditions.

It is true to say that most UV claims are overstated since the specification is provided for a low fish stock in ponds of lower temperature and in a partial shade situation. These conditions rarely exist in climates like yours.

In practice this means if you see a specification based upon your pond volume then by virtue of your location/climate you probably need double that specified wattage.

Click here to review the energy saving UV Clarifiers on my site and solve the problem of how to keep a fish pond clear the most reliable and effective way.

Remove Its Food Source ... Starve The Algae To Death

As noted above and is obvious once you think about it. All living creatures need nutrients (food) to grow. Deprive the organism of nutrients and the organism dies.

Certain types of bacteria in an anaerobic environment consume nitrates and produce nitrogen gas in the process. The nitrogen gas escapes from the water surface and the nitrate levels drop.

By introducing these bacteria and providing areas where anaerobic conditions exist (as is the case in boundary surface layers in all ponds and all biofilters) the nitrate levels will ultimately be reduced to zero.

Under this condition algae cannot survive for any length of time and water remains clear.

This is how Viresco Algae & Blanketweed Solution works ... It is available worldwide from the UK supplier.

As mentioned in previous news letters Viresco really is a fantastic product and will definitely help with algae and blanketweed problems. To find out more about this little known miracle worker take a look here... Viresco Algae & Blanketweed Solution