Solve Pond Algae Problems! Important for Anyone with a Pond Algae Problem
I got an email from Carol in South Carolina this morning and sympathised with her problem. Even though I have written about pond alage problems tens of times I believe that elaborating on why algae forms you can learn how to completely eradicate it. Here's Carol's email and then my somewhat longer response. Anybody with algae (or blanketweed ... a form of algae) problems will benefit from reading this.
Hi Anthony, We do not have "Blanket Weed," but do have algae. We have a biological; filter with a UV light; one that we back wash every three days of so. We have added some chemicals to try to get rid of the algae, but no success. We are in North Carolina and it is really hot so that our koi and other goldfish are not coming up to feed because the water is too warm. We have half the pond covered in either lilies or surface plants such as water hyacinths and lettuce. The pond is about 21/2 feet deep. What else can we do to get rid of this algae, or is the hot weather just too much to try and control it right now. Any suggestions you have would be appreciated.
Carol, Concord, North Carolina, USACarol, Hi
My Reply:
I also live in warm sunny climate so I understand your algae problem.
Your problem is one of the most common in pondkeeping 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 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 cannot 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 favour 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 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).
"Food" or nutrients as far as algae is concerned are essentially nitrates and these are produced by the normal fish metabolic processes.
YOUR CHOICE IS... 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. Plants to some extent help in removing nitrates but never reduce the nitrate to zero levels otherwise the plants would die.
The UV light has one single function. It is designed to kill algae.
The action of an 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 thrugh the UV unit. The living algae is irradiated and killed. If there is enough power in the UV unit to completely suppress algae growth then the water will remain clear.
If the power or irradiating effect of the UV is insufficient then water will remain cloudy.
If an UV is not clearing the 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.
2. Carol, 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 an UV 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.
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 works.
As mentioned in my short message of last week you can download a very detailed explanation of the properties and function of Viresco.
The report also details the results of independent test on various alternatives to Viresco. This report in PDF format is available by
download using this link... Viresco UK
When you get to the Viresco page you will see a link "aquatics' at the bottom of the page ... click this and you will see the download url for the report. It is well worth reading by anyone who has an interest in pondkeeping and especially those who have algae problems of any kind.
UV does not effect aquatic plants.
I discuss all pond problems and how to solve them in my book below.
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