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> > From: Craig Bingman <cbingman at netcom_com>
> > > Where does phenol come from? 
> > 
> > There are many phenolic groups in lignin and its decomposition
> > Lignin is found in terrestrial plants.  Very loosely, it is like glue 
> > that holds cellulose bundles together.  Sort of the collagen of 
> > terrestrial plants.  
> Cellose is the rigid material in macrophytes or what we think of as
> regular plants. The decay of plant tissues, even before the leaves
> detach from the stem, releases phenol and phenolic compounds in very
> low concentrations. Phenol inhibits algaes but it also has an inhibitory
> effect on plants to a lesser degree. It is thought that some plants
> release phenols and other chemicals as a form of chemical warfare
> called allelopathy in order to compete with algae and other plants.
> Straw or hay has been used to clear algae or duckweed from ponds;
> it works extremely well! There are dozens (perhaps more) of phenolic
> compounds including caffeic acid (in caffeine), cinnamic acid
> (cinnamin) and vanillic acid (you guessed, vanilla) which are known
> to have powerful allelopathic effects. Does this give
> you any new ideas for treating blue-green cyano-bacteria?
> One theory to explain why new tanks have more algae problems than
> established tanks is that it takes a while to build up a number of
> allelopathic compounds in the tank. These are thought to act
> synergistically where their combined effect is greater than the
> sum of their individual effects.
> Tannic acid and the humic acids (an extremely diverse class of organic
> compounds) are released by peat or humic soils and these may be useful
> for inhibiting many types of bacteria including cyano-bacteria and
> are fairly benign for your fish. Bacteria themselves engage in all
> out chemical warfare with each other and those compounds can be fairly
> lethal to us (food poisoning) or useful (antibiotics). This is why
> too much uneaten food or a dead fish in the aquarium can be so toxic; 
> this provides a fertile environment for their growth.
> There are a lot of toxic decomposition byproducts from the breakdown
> of organic material especially animal tissue; many of these are products
> of bacteria. After a fish mortality, it might be a good plan to use
> activated carbon filtration but as a general strategy, continuous
> carbon filtration may be counter productive since it will remove humic
> acids which inhibit bacteria. Also humic material and detritus in
> the aquarium also rapidly absorb and detoxify many chemicals including
> zinc, aluminum and copper! Translation: a proper soil substrate is
> healthier than a "sterile" substrate. Humic and organic material in
> soils also performs an extremely important role in the complex system
> which maintains a very stable pH in submerged soils of 6-6.5.
> On the subject of rinsing a filter which has been turned off for more
> than a day, this is probably a wise precaution. I suspect that the
> majority of toxic bacterial products are from anaerobic bacteria
> acting upon labile matter like uneaten food. This is an important
> reason why I keep snails in all my aquariums. I believe there are
> an important part of my artificial bio-systems. To prevent any
> misunderstandings, I don't believe anaerobic bacteria acting upon
> less labile materials such as detritus (the remains of plants) or
> small amounts of carnivorous fish feces are a serious cause for
> concern.
> For further reading on allelopathy, take a look at TAG back issues
> 8-4, 8-5, 8-6 & 9-2 (Walstad); and some discussion in 5-4 (Krombholz).
>  Steve Pushak - spush at hcsd_hac.com - Vancouver, BC, Canada