"Ray" wrote in message
...
I have read a lot here about filter media bio filters and
bacteria, are the plants doing a similar thing ?
cheers ,
Ray.

No,Ray. Plants and bio filters do different things. In simple terms, the bio
filter converts waste to nitrates and then the plants use the nitrates to
grow. Actually the process is more complex than this, but the idea is that
the bio filter and the plants work together to eliminate fish and other
waste. If the fish load is low, one can eliminate a dedicated bio filter
since there will be bacteria throughout the pond environment that will be
sufficient to do the waste to nitrate conversion. Plants to use the nitrates
will always be present. Either you provide desirable ones that are of your
choosing or mother nature will provide plants of her choosing, usually
various forms of algae.
I hope that this over simplified explanation helps.
Paul