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RE: plants and bacteria

>I have posted a couple of questions a few days back and nobody seemed to
>'bite' (granted they were buried within a longer message). One of the issues
>I was trying to raise had to do with biological filtration in planted tanks
>and particularly if we should have it or not. The approach I took was to
>heavily plant the tank from day one and slowly increase the fish load (it is
>still very light) allowing the plants to absorb all the ammonia generated.
>These conditions would prevent the bacteria from multiplying and competing
>with the plants for the available ammonia. What is everybody's opinion on

I recall that for the best plant growth you need 25% of you NH4+ and 75% of
your NO3- coming from your Nitrogen source according to hydroponics folks.
Last I checked plants can't do this conversion from NH3-4 to NO2-3 but
bacteria can. This may be why we need fish and critters to help balance out
things in the Nitrogen cycle for better plant growth. NH4+ is rare in most
every well planted tank anyway. Plants suck it up fast. You'll never stop
the bacteria or limit them much in a tank. You can add extra NO3 by way of
KNO3 but you have to keep up on it and you do not get the same percentage of
NH4/NO3. It is generally far easier for folks to keep a nice balanced
fish/critter population than adding KNO3 all the time but a little of both
can help I think in higher lighted tanks and some of us just can't help but
to push the tank to the limit but the cycles involved are more complex than
adding only KNO3. 
 I was thinking of compiling a list of pros and cons for each case but
>I would rather wait and find out if anybody is interested in this subject
>out there before wasting space and time.
>Adrian Banica.
>Edmonton, Alberta, Canada.

Plants are the filter. There is no competition really due to the nature of a
"balanced tank" and most bacteria don't need light unlike all algae. You are
adding enough so nothing is limited for the plants and the bacteria.
Bacteria (can) use different food source and nutrients than plants also.
They are not like algae which for most of us is a pain in the neck at the
very least. Bacteria will always be there no matter what you try to do<g>. I
think using them to our advantage is the key. Where will they be of most
use? Filtering the water column? No, that's the plant's job. Helping the
organic cycles within the soil? Maybe, perhaps, likely. Beyond water
movement I don't see any *need* for a traditional filter at all. Another
thing is we all mess up our balance sometime. A margin of safety and back up
can help stabilize things. Outside Plant filters/aerial plants, floating
plants can help if you have a CO2 crash(Gee, who hasn't messed up this one
at least once?). Bacterial filters can help some in this area too as they
different cycles than plants/algae and can even the excesses out perhaps.

The bacteria are best kept in the substrate to facilitate the bio cycles
with the plants rather than in the "filter" IMO. Do you want to grow
bacteria or plants? Both can be grown together in the soil but most
"filters" are bacteria only filters, not plant filters. The plants can be in
or out of the water. Using both of them in the right balanced context/place
seems to be the best approach to me. Over/understocking with fish causes
most of the problems, not a competition with bacteria IMO. 

Tom Barr