On Sun, 17 May 2009 10:28:41 EDT, dunns2 wrote:

Hi need some help if possible, I have an Oase Clear Filter 6000
pressurised unit and 6000 Oase pond pump, I have lived in my house for
about 6 years and have never changed the water, you can see on he
picture the water is very green. The fish are mating every year at
least 30 -50 babies per year. I have 2 Koi as you can see in the
picture otherwise the others are all gold fish I think ? I have set up
a quarantine tank so I can start to remove some of the babies and
smaller fish. What I really would like to know is should I be removing
the water and cleaning out the pond from scratch? Bearing in mind this
has never been cleaned for at least 10 years. Is there a good time to
do this?

Hi Steve,

Presumably you clean the filter out as needed and I think this one
flushes itself so you do change some of the water and then top the pond
up. I'm on the text only usenet group so can't see your picture so I'm
guessing at the size of the pond but it does sound as though you may be
somewhat overcrowded in there :-)

The recommendation is to change 10-25% of the water weekly. This is to
get rid of the nitrates that build up and also the dissolved limescale
in the water otherwise it will get to hard. I personally don't
recommend emptying a pond totally unless there is no option.

As for cleaning it, that depends on how much detritus has built up. If
it's been there for a while it's likely to be full of anaerobic
bacteria making hydrogen sulphide and that it very toxic. If you just
net the stuff out of the bottom you will release that and quite
possibly kill all of the fish. A pond vac would be a very useful item
to have to remove this. Alternatively try to get some form of aeration,
(a waterfall or fountain can do that) and take the stuff out one net at
a time and then leave things to settle.

Algae grow because there are either too many fish, they are being
overfed or not enough plants to take up the nitrates. The green water
algae can be cut down by using floating plants or water lilies to block
some of the sunlight getting to the water. If your filter has a UV tube
it decreases in the amount of UV it produces over time and should be
replaced every year according to the manufacturers. The glass shroud
also needs cleaning regularly.

I'm not a fan of UVs because I like to know if there is a problem with
water quality and getting green water is a sign of something not right.
With a UV I wouldn't see that.

As for your question the answer has to be "I'm not sure"/"it depends on
the above" :-)

The first thing to do is pop over to
http://www.practicalfishkeeping.co.u...alculators.php and
work out what your stocking levels should be. It will give you a guide
at least.

Maybe next I'd put a new bulb in the filter so that it can clear up the
green water and I could see what the bottom of the pond is like. Then
either net or vac the stuff out from the bottom. If netting only do it
a bit at a time.

Do a bit of research on vegi-filters and see if it's practical for you
to put one in. It could be a nice attractive extra pond that the water
from the filter runs through full of plants. The idea behind them is
that they take up the nitrates and you keep pulling them out and
composting them. If you can't do that then you need to change the water
at a higher rate to get rid of them.

--
Regards - Rodney Pont
The from address exists but is mostly dumped,
please send any emails to the address below
e-mail ngpsm4 (at) infohitsystems (dot) ltd (dot) uk