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Re: Controllers

> I think Dave was questioning the policy of using a pH
> controller, not the
> technical details.  His question is (and it's a good one);
> your fish
> don't need it, your plants don't need it, so why do you need
> it?
> Two possible reasons come to mind.  You can get it to help
> prevent
> end-of-tank dumps.  Or you could get it to keep CO2 from
> getting too high
> at night.  I suppose you could also get one to amuse yourself
> or to
> relieve yourself of some heavy and otherwise useless cash.

Roger's notions are echoed here. But a pH controller can kill as
easily as an end of tank dump which if you have a needle valve
doesn't happen in any tank I've seen ever.

A pH controlled tank has a higher bubble rate than a tank with
such a controller. It throttles between the higher rate and
shutting off the flow of gas in most set ups utilizing a
solinoid. If it didn't do this and have a higher set rate than a
non controlled CO2 set up then you'd never have it turning on
and off or at least very little. It could never catch up to the
pH set rate if you get it too close, so all have been set higher
than the normal non-controlled bubble rate(no controller-just
setting the needle valve to get a stable pH.).  You can use the
powerhead also to "turn" on or off the CO2(this will overdose
your system byitself but does waste gas) or both in conjunction.
Most folks go with a solinoid since it saves on gas usage
supposedly(I disagree with this idea that it really uses
less-the tank still needs the same amount of CO2 for the
plants). If you set a gas tank plus a needle valve properly it
will do as good as any controller set up. If the solinoid sticks
open as at least 3 have that I personally know of(-not all were
FW plant tanks, one was salt)you will have too much CO2 being
added non stop.....this is as bad as an end O tank dump and
can/has killed fish etc. This is **rare** as is the probe
falling out etc but it does and can happen. Solinoids can stick
open. Another item that I find useless.... 
My point is if you have $ burn it's fine. Fish don't care,
plants don't either. But I have both and see little if any
difference in actual pH ranges(the controller experieces lag
times) so why blow another 100+$ and 40-90$ for a solinoid and
have a more complex set up that is set to over dose if your
controls are messed up by some accident, even if rare? A needle
valve is pretty darn reliable by itself. Simple and cost less
and can be easily adjusted by a very simple turn of the knob, no
soliniod needed and no "another piece of crap to plug in". I
estimated how much CO2 gas a soliniod would save me to justify a
40-50$ soliniod. It's like 5-to 10 years or so. I can live with
that but that's not including the electric. I think the usage
based on a 1/2 open usage came to about 3+$ a year here in CA
where the cost for electric is ever so cheap....:)

Folks should with either/any system have good even mixing and
flow. This will give a much more even & accurate pH and
therefore indicate a truer CO2 level with reduced lag times. 
Tom Barr

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