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Re: CEC and substrate question

In a message dated 6/17/98 3:19:23 AM EST, Aquatic-Plants-Owner at actwin_com
><snip> and if I
>> used an airdriven Reverse-flow setup, which would allow me to extrapolate
>> rates using the dye-marker/time-through-the-tube estimation method, could I
>> not establish both aerobic and anaeobic sites?

(Roger, in hot, dry, brown all around Albequerque)>  
>  Possibly, but its very difficult to control very low flow rates.  A dosing
>  pump would probably give you the best handle on it.

As long as the airstone remains unrestricted, which means regular change-outs,
the air driving the water up to the crossover will be reasonably constant.  If
I ignore variables like evaporation lowering the waterline,  I should be able
to maintain a constant "head" on the downtube, which would give a constant
flow rate.  As for evaporation and the like, there are variables just as
powerful, or even more so in nature.  A certain amount of flux is the norm in
the world, and at this time, I'm thinking the system could live with a little
> I've had trouble with
>  the dye marker method.  When I tried it I couldn't get good results
>  because the marker (food dye) was heavier than water and would sink in
>  standing water.<snip>  

Can I measure the time it takes the food dye to rise through the lift tube,
then measure the time it takes to cover the same distance in the down-tube,
then average the two to get the actual flow rate of the water through the

Bob Dixon