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Overview
Our experience has proven that a
rocked pond will eventually create an anaerobic bacteria bed under the
stones due to lack of water circulation. Anaerobic bacteria, among other
things harbor diseases and produce hydrogen sulfide gas which is deadly
to fish, once released into the water column.
The time frame can be as little
as 6 months to 6 years, depending on your stocking levels, filter systems,
outside pollutants and feeding habits.
If you absolutely love the rock
look, a 1 layer 3-4inch rounded flat river stone , also known as Mexican
River Pebbles will not present you
with the problems you are currently facing and give you water circulation
between the rocks. Remember to keep it to 1" layer.
Under
Gravel filters
We have experimented
and built under-gravel filters with PVC and up flow systems, unfortunately, these
systems will only
delay the inevitable as the holes will clog and the gravel will channel, in as
little as 6 months.
Cleaning
your rocked pond
Your choices for your present rocked
system are limited to removing and washing and sterilizing the rock and
the bottom of the pond once a year (Remove your fish to a holding tank
BEFORE you attempt to remove ANY of the rock) to rid it of the anaerobic
bacteria. Or remove the rock completely forever. Unfortunately these radical procedures
will also remove your beneficial bacteria from the top of the gravel. If
you do this in small stages, the effect on the bacteria bed will not be
as drastic, however, you will have to keep your fish out of
the pond for an extended period.
I would opt for radical cleanout
with a bottled bacteria treatment.
Your filter should also be checked
for channeling and clumps of material since you are eliminating a lot of
the beneficial bacteria bed if you decide not to replace the rocks with
one layer. The best way would be to add a trickle tower after the system.
After
the Cleanout
Once you have done your cleanout,
you should monitor your pond daily for 6 days, by testing the water parameters
PH/Ammonia/Nitrate/Nitrite/ and take appropriate action if the parameters
are out of range .
Reintroducing
your Fish
For the least amount of stress,
reintroducing your fish should be a slow process--replacing 10% of the
water in the holding tank, every day for 4 days until your tests are equal in both your holding tank and pond.
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