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Re: Aquatic Plants Digest V2 #784

> Date: Fri, 20 Jun 1997 14:26:06 -0500
> From: Jamie Howton <jhowton at fotofab_com>
> Subject: Filterless Plant Tanks
> I just read the article titled "Plants and the natural aquarium" by Doug
> Valverde in the July 1997 issue of FAMA.  Doug appears to be advocating
> filterless plant tanks on the grounds that since "plants prefer
> ammonia/ammonium and can use nitrates, but not as efficiently", there is
> little need for filters containing nitrifying bacteria in planted tanks.

Three of my five planted tanks are filterless, and I would recommend it.
Leaving the filter out makes for a simpler setup, and I'm all for simple
things.  But, while I think it should help, I can't prove that leaving the
filter out necessarily gives me better plant growth, and I have some
cautions:  1) beginners shouldn't do it;  2)  if there are fish in the
tank, then be sure the plants are healthy and actively growing - growing
enough that they have to be harvested frequently; 3) its a lot safer for
critters if the pH in the tank is reasonably low (say, below 8).  Ammonium
(NH4+) is nontoxic and dominant under common conditions.  Ammonia (NH3) is
the prevalent form at high pH and is toxic. If ammonium is present and
your pH increases because the CO2 supply shuts down and the plants force
the pH sky high, then the innocuous ammonium can suddenly become noxious
ammonia.  Some tank inhabitants may become former inhabitants.

I haven't found measurable ammonia/ammonium in my three currently
unfiltered tanks.  I tried removing the filter from a fourth tank that was
not well lit and didn't support a lot of growth, and ammonia showed up.  I
restarted the filter.  I've since upgraded the lighting on that tank and
I'm thinking about shutting the filter down again.

Particulates aren't normally a problem, but when the substrate is
disturbed there might be some material left floating about.  It may be a
good idea to keep a mechanical filter handy just for short term use.
Sponge filters would probably work well for that.

Roger Miller