August 17, 2015

Repairing Liner Leaks / Mosquito Fish / Reader Response

Today's Pond Q&A

In this issue:

- Repairing Liner Leaks

- Controlling Mosquito Fish

- Reader Response to Duckweed Question

- Reader Response to Using Malathion to Control Aphids


Question #1>

Hi Carolyn,

Is there any way to repair a leak in the liner without emptying the
pond? I have heard that you can add bentonite agitate it and as the
leak pulls it in the bentotite will seal the leak.

Have you heard this? Thanks for any help you can give me.


Answer #1>


I think that really depends upon the leak, how big the hole and
where it is located. I certainly wouldn't want to trust a hole in
the bottom of my pond to a clay remedy. In fact, I have heard that
many natural ponds are lined with bentonite clay to contain the
water, but I don't think the idea of repairing a leak with clay
will hold water, no pun intended.

I have a pond and a waterbed. That said, I would repair both the
same way. I dry the area around the hole, use alcohol to clean
it, and then apply a contact cement. To this, I apply a piece of
liner and hold until the glue sets. Then I would not refill the
pond until the glue has set for at least 12 hours.

It is similar with a waterbed except that the patch is on the
outside and the water is inside, and you hope you can keep it in
while the glue sets. At any rate, you don't go to bed until later
that night when you're sure it isn't still leaking. In the same
way, watch the hole you patched on the pond liner for any sign of
leaks, or air bubbles, when you refill the pond.

Luckily I have only had to repair one leak in my pond liner because
the algae and bacterial growth can make it very difficult to clean
thoroughly for a good seal.


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Question #2>

Hi Carolyn,

Thank you for all your help. I really appreciate your including me
in your e mail.

My question this time is: Is there any other reason to have
mosquito fish in a pond other than eating mosquito larvae? They
multiply so quickly that I must have thousands in my 20,000 gallon
pond. I think they are a nuisance; they scare away the other fish
at feeding time and I wonder if they are contributing significantly
to waste deposits in the pond.

How can I get rid of them. When I cleaned out the pond in the
spring, I thought that would take care of them, but it didn't phase
them that I can tell. Doesn't keeping the water circulating all
the time keep down the mosquito population?

I'm so new at this, I am really grateful for your help.


Answer #2>


I have never actually put mosquito fish in a pond for mosquito
control. Generally, I prefer to use them in bog gardens and water
gardens that aren't filtered well but are heavily planted. I
prefer to use Microbe-Lift/Biological Mosquito Control in the pond.

I should agree with you that any fish, even small ones, will
contribute to the bio-waste. Depending upon where you live, the
mosquito fish will or will not live through the winters. We have
had them live through winters in NY if in a deep enough pond, like
yours, but in bogs that are shallow, they die back.

I would think they might make a nice meal for game fish instead of koi.
Koi and carp don't eat their own. Maybe try a very fine seine net?





Hi Carolyn,

I enjoy your pond q/a emails. Thanks for doing this!

I am the water plants person at a nursery here in Menlo Park, CA
(Bay Area, peninsula) where we have a koi pond and several smaller
water features. My experience with duckweed is that during the day
when there's plenty of light it adds oxygen, but if the entire
surface is covered it can somewhat deplete oxygen at night. Like
all green plants, duckweed produces O2 in the light and consumes it
in the dark.

In my experience, if a pond is at least a foot or so deep and there
are not too many fish, a cover layer of duckweed is not a problem
at night. But if the pond is quite shallow the O2 level can drop
at night if there's a solid cover of duckweed.

I hope that helps...!


Hi Carolyn,

Someone put a bottle of "malathion 50 plus" in my KOI tank. My tank
is a polyethelene 1100 gal tank. There were 17 KOI, 5 african
cichlids and 1 pleco in the tank. All of them died.

I called the police to report it and they called HAZ MAT and the
fire dept. The fire dept and Haz Mat declared my tank a toxic site.
Haz Mat and the fire dept pumped out my tank and took my fish (
toxic waste ) and told me my whole system would never be fish safe

I called Chevron Chemical and Ortho the manufacturer of malathion
and their engineers told me the half life of malathion was forever
(it will not break down ever), and the fatal dose for aquatic life
is so small my tank and my filter (Ultima II 200) and the plumbing
in the system will never be fish safe again.

For now I guess this has killed my fish hobby. I lost over $5000 in
my KOI alone.

You want to be very cautious using any pestisides around a pond.


Carolyn's Answer>


I think I told them to remove the infested plants from the pond, use
the chemical, and then rinse well before returning it to the pond.

In our area of NY they have been using a diluted malathion spray in
an arial application to try to stem the tide of West Nile Virus.

I should have recommended Insecticidal Soap to be used in the same
way, as a dip for the aphid removal, then rinsed before replacing
the plants in the pond. As always, you should read labels and follow
the directions carefully before attempting any new procedures.

Thank you for sharing that painful experience with us.


========== @SK Carolyn =================
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Happy Pondkeeping!

Brett Fogle
MacArthur Water Gardens

Posted by bfogle at August 17, 2015 06:59 PM