garden pond

[kopend]

i know i have asked about ponds on here in the past
but i was helping my mum to clean her pond last night - without much success
we emptied quite a lot of water the cleaned out as much green sludge as we could - and then re filled it - but it looks no cleaner to be honest! she says its get even worse when the sun shines on it and puts that down to not having as many lilleys on the top as she had last year - and ideas - magic plants or snails perhaps???

[SlackAlice]

Need to know a bit more about the pond.
Location, sunny, shady?
What size in capacity and rough dimensions?
Any fish, sizes and number?
Apart from lilies any other plants, marginals, oxygenating plants?
Any filter/uv running?

The green colouration of he water is basically alga, and the major cause of this is nitrates in the water. Reduce the nitrates and the water will clear. Unfortunately, tap water generally contains nitrates as well so re-filling a pond isn't a quick fix.

[paddywak]

Have you got any filtration system with the pond? A good UV light and filter can make a big difference, but as Alice says there are many factors involved and we'd need to know a bit more.

[kopend]

the pond is about 12 foot x 8 foot

and about 3 ft deep

it has about 6 gold koi carp in it (about 6" long some longer)

and ten "black" fish again about 6" long - some smaller

its in a garden with trees at the back of it

[rowanwitch]

you need a big filter with a uv light in if you have Koi they produce huge amounts of poo which feeds the algae

[SlackAlice]

A pond of that size equates to about 1800 gallons brimfull. You would need at a minimum a pump/bio filter system capable of turning over that quantity of water per hour in the summer. Aim for a pump of 2000 gallons per hour to cover pump losses due to bends/joins in the pipe. Additionally you would need a uv light of a minimum of 20watt.

Fish produce nitrite in their waste products, the more you feed the more nitrite produced, do not overfeed them, (in fact keep them mean and lean!). Nitrite is converted in the water by bacteria to Nitrates. Nitrate is used by plantlife for growth. Growing Marginal/Submerged plants uses the nitrates up. Insufficient plantlife means excess nitrates left in the pond. Green water is just Algae in suspension. Algae needs water, sun and nitrates to grow and multiply. Algae can be killed by UV light.

All ponds are overstocked with fish in terms of size, number and type. It wouldn't be much fun with only one or two fish in 1800 gallon pond! My pond has more fish than yours but is smaller. You have to artificially assist Mother Nature to balance the pond.

Before you do anything else consider buying a water test kit from an Aquarium shop and test the water to see what the levels are, you should be aiming for an almost neutral reading. The kits are not very expensive.

Your lilies are almost certainly being eaten by your Koi. I've given up trying to grow Lilies my Koi somewhat bigger than yours take great delight in eating the leaves as they start to grow.

Encourage some floating plants, because they will add shade and use nitrates. Do not buy 'Fairy Moss' though because this is highly invasive and grows like 'billy ho', nightmare to remove and eradicate. It would swamp a pond within a few weeks and would take about 2-3 yrs to eradicate, I know this from bitter experience!!!

Best of luck ☺