yup. high pH, bring it down. however. baking soda blows off as CO2, need dolomitic
limestone in the pond to increase hardness.

whenever there is suspicion of poisoning start running water into the pond one end,
let it overflow the other. If this is city water then need to have some kind of
regulator like MELNOR AUTOMATIC WATER TIMER cheap, set it for X gallons and add
dechlor (get buckets of this from aquatic ecosystems, sodium thioglycolate).

INgrid

On Fri, 27 Jun 2008 02:23:53 -0500, how wrote:

Christine_B wrote:
I have recently had a company edge the pond with stone.

In carrying out this process, five tench I had in the pond have died.
After the work was carried out they were initially distressed, and
sadly died towards the end of the day.

I can only surmise that the cement from the work has entered the pond
in sufficient quantity to cause polution? Is this a likely cause?
There is also other wildlife living in the pond, newts frogs etc, and I
am worried as to the effect the cement has on them.

What is the best way to go about cleaning up the pond so as not to
cause any further harm to the remaining wildlife?

Hi,
Fresh concrete can upset the pH of the pond rapidly but (depending on
how much fell in) you can probably make adjustments. First if you do not
have a method to determine pH, GET IT. Get tests for KH (total
alkalinity) and GH (general hardness) also.
Get all the concrete possible out of the pond, assuming that some fell
in. If the new edge is under water lower the pond level temporarily.
I don't know what tench prefer but a stable pH is usually more desirable
than a particular number. There could be other problems, perhaps they
spilled something else in the pond.

If KH is high (above about 200 ppm or 11 degrees) and pH is high (above
9), then use muriatic acid. Available at hardware and pool supply
stores. Put 2 oz. acid in a five gallon bucket, fill with pond water,
and disperse it throughout the pond. A dose of 2 ounces per 1000 gallons
lowers KH by 1 degree (20 ppm) releasing it as CO2. CO2 suppresses
respiration in fish, so the pond should be well aerated. Next day the
pH and KH is tested again. Once KH is lowered, pH will follow. It
shouldn't be necessary to lower KH below about 150 ppm (8 degrees). Two
oz. per 1000 gallons is the maximum daily dose.

If KH is low (below 100 ppm) and pH is high (above 9), instead add
common baking soda. One-quarter pound per 1000 gallons increases KH
by 1 degree. Once KH is 100-150 ppm (6 to 9 degrees), pH should
stabilize near 8.4.

You will have to keep monitoring and treating.

HTH -_- how