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Re: flow in the substrate

On Sat, 22 Apr 2000, Tom Barr wrote:
> But aren't bacteria's needs very small too? They may just take a
> proportional amount longer to react than the filter bacteria? And this
> slower rate adds to the cycle in slow small amounts which is good for the
> plants and keeps the algae at bay? Wouldn't a shock to a tank like this (no
> filter) take longer to rebound than a tank with a plant or bacterial filter
> also?

Bacteria are very important to conditions in the substrate.  The
relationship between plants and soil bacteria is very nearly symbiotic
(actually symbiotic in the case of legumes).  In our aquarium setups the
plants may be very dependent on bacterial action, or relatively less so
depending on the nature of the substrate and the amount of substrate

Probably the highest degree of dependence (really, interdependence) occurs
when circulation is very limited.  Nutrients are then supplied by very
gradual water movement, by digging and/or burrowing animals and (in a
coarse substrate) by detritus sifting gradually down through the
substrate.  Under those conditions, the chemical environment in the
substrate is determined by the relationship between the plants and the
bacteria in their rhizosphere.
> OK, now what about those pesky RFUG's I use? They have lots of flow almost
> to the point of fluidized bed filters. And they grow plants very well like
> no flow substrates. Then there's the heating cables. These act as both
> filter and substrate.

Your filters provide for the circulation of water carrying both oxygen and
nutrients from the water column directly to the substrate.  The flow
promotes more aerobic bacterial activity, which means more bacterial
activity overall.  There are probably substantial differences between how
plants get nutrients in a no-flow substrate and how they get them from
a substrate with circulation, but either method works.

Roger Miller