Re: Estimative method/Barr method

[Thomas Barr <tcbiii at earthlink_net>]

> With high GH and KH and pH tap water, a 40-60% water change is taking my
> CO2 down to around 5 ppm (or whatever normal ppm is without supplement).
> It takes about 1-2 days (sometimes more) for the pH to recover to the
> 7.1-7.3 range I try to keep it in.

A decent CO2 system would keep the pH in a good range within 1 hour or so.
If it takes days to hit a good range, how is it that the system is able to
keep up with the plant's uptake depletion rates?

CO2 is the biggest issue for you. And it will cause the most grief if it's
not well set up and responsive.

 With my previous water change
> regimen of every 2-4 weeks a 2 day drop in CO2 (rise in pH) did not seem
> too bad (only 5-10% of the time).  With a weekly water change it will
> now be for about 30-35% of the time or more.  This means the CO2
> concentration is moving to around 5 ppm for around a third of the time.
> Occasionally I might have to do a water change after only 4 days because
> of other obligations (yes there are other things besides fish and plants
> though my wife might suggest I think otherwise - however I do enjoy this
> a lot) and that could mean the CO2 level might be down below 10 for
> quite a while.  If I had to change water after 4 days twice or more in a
> row the tank would have the desired CO2 level for only 20-25% of the
> time.  That would almost be the same as not having CO2.  In a high light
> tank this would seem to me to be a bad thing.  From what you have said
> about CO2 and algae, I could imagine this being a really bad deal with a
> lot of light.  As I recall from my early days at plants

It should not be an issue. Add more flow through the CO2 diffuser/add more
circulation ton the tank, get something that mixes the CO2 better/faster etc
etc.

> 1)  It is not a bad deal.  I know, the plants adapt and with the right
> nutrient levels it will all work out without a lot of algae.  The key is
> getting the nutrients right, the low CO2 levels will just slow plant
> growth for those periods it is down.

No. 
 
> 2)  Your CO2 system returns to the desired value much quicker than mine.

Well not just mine, just about everyone else's.

> This would make me think there is something wrong with my CO2 system:

Me too.

> the reactor needs cleaning more often than I am doing it; the water flow
> is too high for good exchange; and/or the water flow is too low to pump
> enough CO2 into the tank.

Too low is far more likely. More will not hurt unless the unit is burping
out gas bubbles etc.

 I know that everyone's circumstances are
> different (tap water GH, KH, pH, and w/g, fish and plant load and needs,
> etc.) but I suspect that this is probably where my tank differs from
> most of yours and is the area I should look into first.  After you do a
> 50% water change, how high does your pH go and how long does it take
> your tank to come back to the desired pH?

About 1 hour or so.
 pH, KH, GH of the tap etc really doesn't matter. It's all about the
CO2/uptake/mixing rate/flow rate etc.
 
> 3)  I should make the water I add during a water change more like the
> water in the tank (something like add CO2).  It seems logical to make
> the water you add as close to the water in the tank as possible.  But I
> have never seen mention of that here and judging by the 'minimum effort
> to get great results' attitude many here seem to have I would suspect
> that either this is not the case or it is such a given no one talks
> about it any more.  Is it worth adding CO2 to the change water?  This
> seems like a bit much but it would not be hard to add a tee and a
> reactor (have an extra one) to the closed container I use to mix change
> water.  Do you add something else for pH?  Wouldn't that affect the
> pH-KH table?  That also seems to contradict about everything I have seen
> here.

No. Don't do this. CO2 only. Never monkey with pH except with CO2. If the KH
is 2-3 or above, you only need to add CO2.
 
Regards, 
Tom Barr