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Correcting Phosphate accumulation

Discussion in 'Water Features' started by PSUhardscaper, Jul 16, 2011.

  1. PSUhardscaper

    PSUhardscaper LawnSite Member
    Messages: 80

    I'm new to the pond game - I had a family friend ask me if I could figure out why his pond didn't seem to have the 'life' it once did.
    fish are not reproducing
    plants are slowly dying off

    I bought a pond text kit and it tested high in phosphate levels. Homeowner fill the pond with tap water every night so I tested that also. Not nearly as high as in the pond, it was at typical levels for tap water. (pond came in at 2ppm).

    pH, nitrates, and ammonia all checked out OK.

    I am wondering what I can use, other than phos-out, (or in conjunction with phos-out) to lower the high levels of phosphate - I am thinking of plant material. Suggestions?

    Thanks guys.
  2. RussellB

    RussellB LawnSite Fanatic
    Messages: 8,535

    I beleive I would change out half the water and clean the filter prior to adding chemical or additional plants. I have water lettuce and water lillies along with 10 koy in my pond and (knock on wood) it has remained healthy.
  3. tadpole

    tadpole LawnSite Bronze Member
    Messages: 1,221

    You state that the pond is high in phosphate, yet you also state that the level is 2 ppm. Anything less than 5 ppm is acceptable
    Why is the owner adding water every day? Does it have a leak? Is he using a 'Dechlor'. Has a herbicide or pesticide application been made anywhere in close proximity to the pond? Has or are they using any other chemical treatment in the pond? Is the pond have an excessive fish load? What are the specs of the pond-surface area, depth, capacity, sun, shade?

    What is the sediment level on the pond bottom? When was it last cleaned?

    These are just some of the questions that need to be answered in order to get any valid reply.
    Last edited: Jul 16, 2011
  4. cindyb

    cindyb LawnSite Senior Member
    from KY
    Messages: 354

    They need to be changing out 10% weekly with a chloramine buster to take care of the ammonia/chlorine in the water. Topping it off isn't the same. Are they doing flushes of their biofilter? Especially in this heat.

    Test kits. Tell me the numbers, I could see something you don't.
    You need to check ammonia, ph, nitrites and kh. A seasoned pond filter and an overload of fish with low filter maintenance, can eat the kh or total alkalinity causing the ph to drop and cause major problems.
  5. Fishwhiz

    Fishwhiz LawnSite Member
    from Oregon
    Messages: 112

    Those phosphate levels are approaching the low end for raw sewage. Phosphorus unto itself is not a concern for the fish, but since the pond plants are suffering in-spite of ample fertility, your problem is more likely acidic soil. Most plants suffer at pH ranges below 5.5
  6. PSUhardscaper

    PSUhardscaper LawnSite Member
    Messages: 80

    Here are the test kit results taken on July 15:

    pH: 7
    Ammonia: 0ppm
    Nitrate: 0ppm
    Phosphate: 2ppm
    Phosphate level taken from tap water used to fill pond: .25-0ppm

    I would say that the pond is about 10' long, 3' wide and an average of 2' deep.
    It does have a waterfall feature at the deep end.
    There are about 15 6" goldfish (koi?) in the pond which have ceased to reporduce. The H.O.'s comment was that the ecosystem just seems 'off'.
    I am a hardscaper, I'm just looking at this pond as a favor to the pastor of our church. Any/all advice is appreciated.
    Thank you.
  7. PSUhardscaper

    PSUhardscaper LawnSite Member
    Messages: 80

    There is a slight amount of 'slime' on the rocks at the bottom of the pond but no excessive algae. I do not know when it was last cleaned. There have been no other chemical treatments this season. The pond is shaded.
  8. tadpole

    tadpole LawnSite Bronze Member
    Messages: 1,221

    Based on the test results that you posted, the pond looks to be in balance. The only result that jumped out at me was the NitrAte level of 0.00. There is always some level of NitrAte in a pond. Could this be the NitrIte level instead?
    With 0.00 NitrAte, the plants have a very limited source of nutrients. As a result they will begin to look puny and die, much like their terrestrial cousins. He may need to start fertilizing the plants.

    The Goldfish (Koi?) are probably spawning, but they are eating the eggs and the fry before they can develop (Koi eat only the eggs). Based on the ponds specifications, he has one fish for each approx. 30 gallons. This is pretty crowded, which explains why there are no new fish.

    Phosphorus levels are good. No problem there. The slime that you refer to is a beneficial biofilm that forms on all submerged surfaces. It is beneficial.

    How shaded is the pond? Aquatic plants do require at least 4 hour of sunlight to retain vigor.

    Can you post any photos of the pond?
  9. PSUhardscaper

    PSUhardscaper LawnSite Member
    Messages: 80

    I will take some pictures this week and post them. Also, in a previous post, Fishwhiz stated that my phosphate levels are approaching the low end of raw sewage... but you have said they're OK. I'm not sure what to make of that.

    My mistake: looking back, I tested Nitrite levels, not nitrate.
  10. tadpole

    tadpole LawnSite Bronze Member
    Messages: 1,221

    Fish Whiz posted that ridiculous statement without even knowing what the actual Phosphate levels were (You had not posted the actual test results up to that point) I read the statement and chose to ignore it as being ludicrous.

    0.00 for NitrIte is as good as you can get, but you do need to test the NitrAte levels. It sounds like the plants are lacking either nutrients and/or sufficient sunlight, unless they need thinning. Plant overcrowding will cause a decline in growth and productivity. If they are in pots they may be rootbound.

    Google 'water quality, phosphorus' and you will find exactly what I previously stated---P levels less than 5 ppm are acceptable.

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