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Re: controller

> A pH controller also makes a pretty good safety switch when your CO2 rate is
> set to match (or slightly exceed) the tanks daytime consumption. The only
> difference is the controller decides when to shut off the CO2, not a timer.

You can use a pump also in placed of a solenoid although it will waste the
gas unlike the solenoid.
> A couple years ago, I had a ballast fail while out of town. With the
> lighting cut in half, it could have been ugly after a few days without the
> controller cutting off the CO2.

I've had the light bulbs fail and saw little ill effects over the short
term. Never lost any fish or had any algae result from that. pH was a little
lower, no disaster.
> Controllers are not required, just convenient.

I fiddle less with a non controller set up than a controller set up and for
the extra 100$ over a monitor, that's not too convenient for me personally.
>> Well think about it. The sump is where you have a small area
>> with great
>> mixing and the CO2 inflow. The tank is where the CO2 is being
>> used up and is
>> much larger and slower flowing. Where are your plants? The
>> sump or the tank?
>> That's the best place to take the reading but there will be
>> some lag time to
>> get the pH up after turning it up or down etc. This becomes
>> more true as the
>> tank gets bigger. Well mixed water helps solve this problem
>> among others.
> I'm only seeing a 0.04 range between my sumps and 6 locations in the tank.

A tank with 3-4 times turnover per hour with good circulation patterns is
sufficient. Your CO2 reactor is INSIDE your tank(unless you've changed
that). So the sump issue is not much issue. You have 2 pumps returning and
two overflows. You've got a well run and prepared tank and account for the
breakdown of things. I like Techy stuff and all but am more practical at
home. Your CO2 rich water appears to go in at the bottom(like it should IMO)
and the CO2 poor water is sucked off the top and filtered. The range you
have with what flow regimes you have sounds right. Most folks add the CO2
reactor to the sump.
A nice flow of CO2 rich water from bottom to top is _ideal_. It travel up
through the plant's leaves giving the CO2 gas as it passes by. You have this
flow pattern.
Some folks don't or add/delete something and have poor mixing.

> How large of a range are you seeing in bigger tanks? I don't consider my
> circulation rates very high, yet I get pretty consistent mixing.

You have a good design. Some tanks have measured .2 to .3 units off. This
was solved by adding a larger pump to the reactor and adding a spray bar or
in one case adding a larger return pump. Then the differences were removed.
Sometimes is was the reactor method itself in which case it was replaced.
This would give the controller a better chance at hitting the targets by
doing this. + or - .1 pH unit is acceptable IMO for a controller.
Some German companies made controllers with lag time controls to take this
into account. From a practical stand point this is not need for plant tanks
Your tank still looks great. Love the nice clean organized sump. Nice to see
some folks still have Sandpoint stuff.
Tom Barr
> Jon Wilson
> http://www.knology.net/~jwilson/plants.htm