Re: substrate flow rate

> Charles Bay wrote:
> >  - Steve wrote:
> > Here's my concept: what if we take some 1-2" dia PVC tubing and fill it with
> > sand, organic material and laterite [snip]
> Can we use the sand (or whatever) inside the tube PRIMARILY to slow the water
> rate to the substrate from a power head for slow flow rates?  Or are we just
I don't think I'd suggest a power head at all. When I said head I really mean
hydrostatic pressure which is the same as saying the difference in heights
of two bodies of water. In the soil, this flow is very slow, perhaps in terms
of drops per minute (or hour). I'd just use the natural pressure available
by catching some of the outflow from another trickle filter and spilling all
but a few centimeters or millimeters of that away. The flow is so slow as not
to be perceptible.

                                     |   drops of water
                                 ||  O |  ||
                                 ||    O  ||
_________________________________||*******||^ water level in tube +.5cm
             ^ tank level        ||*|**|**||<-- tube

> fighting ourselves?  Of course, sand compacts over time (if not mixed as you
> suggest with peat, laterite, etc).  Maybe we could look at vermiculite for 
> the fill.  Although it's a ?silicate clay, I don't think it compacts much 
I'd use sand to maintain porosity. Don't see much use for laterite in the
tube though. Better in the substrate where the roots can touch it.

The tube should be clear plastic so we can observe what's happening inside
and removable for maintenance. The outlet end should contain sand to act as
a filter to prevent fine particles from escaping. The inlet end should 
contain a small amount of peat I think and the middle should be a mixture
of clay and sand (to prevent compaction). The higher the compaction, the
more controllable the flow rate is because we are free to use much higher
differences in inlet vs. tank height (water pressure)

> Do we really need the organic material if we're adding iron supplements right
> to the substrate?  I know lowering the pH may increase the available iron,
> but what if our supplements are already in available forms (Dupla drops)?   If 
> the substrate has a lot of CEC and we add directly to the substrate, I'm hoping 
> the iron goes right to binding on an exchange site.  (I just seem to have a 
> hard time adding soil/peat to the bottom of my aquarium, even though I know 
> this is what nature provides.  I'm nervous about 
> disease/mess/maintenence/decomposition in this "clean" hydroponic environment, 
> and I know that carbon-based wastes will build up over time anyway.)
The peat is necessary to provide humic acids. The idea is to provide a
uniform source of iron nutrients preferably at low cost. Let's face it,
the cost and trouble of daily iron feeding is high. The concept is to 
duplicate the Dupla process without heating cables and hopefully without
Dupla drops. How come you need drops anyhow if you have Laterite?
With this concept, the ONLY place peat is needed is in the leaching tube,
where it can easily be removed if the situation takes a turn for the
worse or needs to be maintained. A tube guarantees uniform controllable
low volume flow without adding heat and confining organics to a much
smaller and manageable place.

I would appreciate information anyone has on the iron chemical processes.
Technical is ok. Is it possible to reduce iron oxides or silicates
safely at a certain pH, temperature? What state is micronized iron?
How about metallic iron like a nail? Is this "safe"? What sources of
iron could we use that would be low cost? How about RUST!? Any good

> Finally, I've come full circle and am now wondering why I hate RUGF/UGF so
> much.  In slow flow rates, it seems to be the only (real) alternative to
> heat coils for keeping a 4" substrate from going anaerobic.  
Yeah, or don't put too much organic material in the substrate. If you tear
down your tanks every few years, it might not be much of an issue.

Too bad we don't have aquatic earthworms! ;-)

 - Steve (just a different email address)