Help!
My Water Has Turned Green!
by Ray Jordan
I get lots of phone calls this
time of year from pond owners distressed by having their pond water turn green
which prevents them from seeing their fish. I have listed below some potential
solutions to help get rid of the pea soup and clear up the water in your pond.
A population explosion of
microscopic single cell plants called algae are the reason your water turns
green. This is also referred to as an algae “bloom.” These “blooms”
happens most often in the spring and especially in new ponds as they start
through their maturation process. These tiny plants have the same requirements
as most other plants. They need sunlight, nitrates, carbon dioxide, oxygen,
certain minerals, and water. If you deprive the algae of these necessities they
will disappear. Before we explore some tactics that will help rid your
pond of the green water curse it is important to mention a few things about pond
filtration. First, I do not know of any practical filtration system that can
eliminate planktonic algae. Second, a poorly designed or inadequate filtration
system can increase the likelihood that you will have problems with green water.
Buy a set of pond test kits for Ammonia, Nitrite, Nitrate, and Oxygen to be sure your
pond water is healthy for your fish. Also, there are chemicals that can treat
the algae in your pond however, you are treating a symptom and not the cause of
the problem when you dump a bunch of chemicals into your pond. Read the
instructions if you go this route to be sure they are safe for your fish. Be sure you really know the accurate gallon capacity of your
pond instead of your pond builder’s “estimate”. Most people over estimate
the size of their ponds by a factor of 50% to 100%. If your pond is only 600
gallons and you treat for 1500 gallons you could kill your fish. The only
accurate way to be sure of the size of your pond is to drain it and then fill
while recording your water meter reading at start and finish. Do not use any
water elsewhere while you fill your pond. The meter records cubic feet. To
covert to gallons multiply by 7.5.
I believe it is much better to fix the reasons you are getting green water than just try to kill the algae and potentially cause worse problems to occur.
Sunlight: Reduce the amount of light that strikes your pond. Use plants like water lilies in your pond to shade about 60% of your pond’s surface. Use landscaping such as trees or shrubs to shade your pond. Be careful of overhanging plants as they can drop leaves and other stuff into your water and cause other problems. Build a trellis or arbor to shade your pond. Again be aware that if you have light loving pond plants you do not want to prevent them from thriving. This is one of the biggest challenges of trying to keep fish and plants together under the optimum conditions for each. Most plants need lots of direct sunlight. Green water is cause by a microscopic green plant and when too much sunlight is available it can cause algae blooms.
Nitrates
& Minerals: Nitrate is the end product of the nitrogen cycle
that is critical to allowing you to keep your fish healthy in a closed environment. Fish produce ammonia which is
converted by beneficial bacteria into nitrites and then by another type of
bacteria into nitrates. The first
two compounds are poisonous to fish while nitrate is relatively harmless except
at higher concentrations (above 20ppm). Minerals that plants need are supplied by fish
waste and decomposing materials like leaves, etc. Nitrate is also necessity for
plant growth. The more fish you have and the more you fed your fish the more nitrate is produced. Also, uneaten
fish food is broken down into Nitrate and adds to the problem. This is another
very good reason to not over feed your fish. Also, it is very important to reduce the amount of nitrates
by doing regular water changes about 10%-20% each week minimum. During an algae bloom if
you do water changes of about 25%-40% several times a week, you will quickly see
an improvement in water clarity. Do not
forget to use declorinator. Another issue is the fertilizer pellets you
might be using if you keep potted water plants in your pond. Do not fertilize
too often and quit if you develop green water. Be sure fertilizer pellets are pushed way down in the soil
in your pots. Cover with rocks to prevent koi from exposing them to the water
directly which can cause another algae bloom. Some bog type plants that are living in your
pond will also compete with the algae and reduce the amount of Nitrate
available. Plants growing in soil like lilies and bog plants help but the best
plants to remove nitrates are submerged plants like elodea or filamentous algae
(blanket weed) that grows on the sides of your pond. It is thought that
filamentous algae may secrete a substance that retards the growth of platonic algae
as a way to insure clearer water and therefore more sunlight for themselves.
Carbon
Dioxide and Oxygen: Plants such as algae use carbon dioxide and give
off oxygen during the day. However at night they use oxygen and give off carbon
dioxide. This is why fish kills happen at night or early in the morning when
oxygen levels are at their lowest.
It is often said that green
water is good for your fish but bad for “viewing” your fish. This is not
true if your fish do not have adequate oxygen available. Be sure your pond water
is saturated with oxygen if you have fish. This topic could be a separate
article. Be sure your pond has plenty of aeration. This is supplied by using a
air pump and air stones or a waterfall or better yet, both. A higher level of
oxygen in water reduces the amount of carbon dioxide and the reverse is also
true. Additional water plants also compete with algae for carbon dioxide in the
same manner as with nitrates.
Water:
Eliminating
water would not be a tactic I could suggest.
UV Systems: Systems using special Ultra Violet lights are made specifically to kill planktonic algae in ponds. These units can be very effective when sized correctly but are not inexpensive. The UV light kills the algae by affecting their DNA so that they die very quickly. UV units work and work quickly but it is very important that you set up the system to treat all the water in your pond at least every six hours to be effective. These units come with specific recommendations concerning total pond gallons and water flow rates through the unit. Buying up one size is a good idea. The UV bulbs have to be replaced once or twice a year to be totally effective. Many hobbyists only run their UV units in the spring when algae blooms are more likely. Remember that something is out of balance and causing excess nutrition and therefore green water. If you use a UV system to clear your water you still need to identify and correct the underlying cause of the problem. If you kill off the algae and there is still a lot of nutrients in the water you will encourage bacteria populations to explode and some of these bacteria can begin to infect your koi as well.
Barley
Straw & other Stuff: I have read about using barley straw and other chemicals to get rid of green water algae. One commonly sold chemical dyes your
water blue to cover up the green. It reduces the sunlight but is really more of
a cover up and you still can't see your fish. When you drain and refill your
pond the original problems that caused green water are still there so it starts
all over again. If you want to try some of these 'treatments" check
out articles on different websites like www.AKCA.com and please be especially
careful adding chemicals to your fish pond that are supposed to kill algae.
Summary:
There
is no reason you cannot have clean and clear pond water provided you try the
steps listed above and give them ample time to work. If your pond is in full sun
and you want to have your water lilies bloom profusely you may need to install
an UV unit and limit the amount of fish and food you feed your fish. Try to combine the suggestions listed above to maximize their
effectiveness. Do not expect dramatic over night results. Natural methods will
work but take time. Four to eight weeks might be required. If you are impatient
for clear water go for the UV system but you still need to reduce the number of
fish and amount of food you are feeding.