Continuous water changes

[Trapper]

Howdy folks,

I'm going to be setting up a biggish tank soon, and I'm going to have
to perform water changes with water deviant in several important
respects from tapwater. Thus, I will have to keep a mix of the stuff
brewing in advance.

Logistically, I can't see keeping more than about 10 gals of water
change water on hand pre-conditioning etc.

Given the size of my tank will likely be north of 100 gals, and that
I'm likely to want to do, say, a 25% weekly water change (25 gals)
this leaves me in what at first seems like a pickle. Namely, the
pickle is not having enough water to complete the change.

So, the first thing that popped into my head is to just do maybe 3
smaller water changes during the week. The amount to be so changed
will be such as to equal, after the third change at week's end, the
net effect of a 25% water change.

My calculation for a 100-gal tank is that you change about 9.14 gals
three times. This is, remember, an amount less than the 10gals I'll
be able to make in a day. The math is:

(v) = t - (t * ((f)^(1/n)))
where:
v = volume to be changed
t = tank volume
f = fraction of original water to remain
n = number of water changes
Here 9.14 = 100 - (100 * ((0.75)^(1/3))).

Hrm, interesting, I thought. You see where this is going, don't you?
:)

As above, I said "let n=168*60", the number of minutes in a week. The
result is something like 11 ml per minute.

I'll likely be running a wet/dry filter and CO2 injection. Given the
above, I plan simply to withdraw ~4 gals of water from the system in
the morning (the w/d will, I hope, continue to run in a system down 4
gals) and then start dosing with the pre-made water-change water at
11ml/minute. I'm guessing a good CO2 reactor will be able roughly to
keep up with the addition of water at this rate, and that as a result
the [CO2] and pH swing experienced in the tank will be less than if I
were to dump 25 gals of conditioned (but not CO2-injected) change
water. There won't be stress on the heater, since the water will be
preheated.

An additional advantage, I think, is that I can put a daily dose of
fertilizer in with the ~4gal of daily water change water, thereby
giving my plants a nice even feed throughout the day/week.

On paper this idea seems like a real winner. Still, I haven't really
read about anyone doing it. This makes me think there's a hidden
gotcha somewhere, but I'll be darned if I can see what it is.

What say you?

--Trapper

[Brian S.]

That sure seems like a lot of work and figuring for easy water changes.

While I understand that you want to do it slow so you won't bother the PH,
but if you are talking about 10% water changes three times a week, I don't
see any harm in just siphoning it out and then dumping 10 gallons in.

If you are going to add 11 mL a minute, you are going to need some fancy
equipment that will measure this.

In addition to that, you may run into a problem with your tank actually
flooding over if you add more than the tank can handle.

Just some thoughts...

Brian S.

"Trapper" > wrote in message
om...
> Howdy folks,
>
> I'm going to be setting up a biggish tank soon, and I'm going to have
> to perform water changes with water deviant in several important
> respects from tapwater. Thus, I will have to keep a mix of the stuff
> brewing in advance.
>
> Logistically, I can't see keeping more than about 10 gals of water
> change water on hand pre-conditioning etc.
>
> Given the size of my tank will likely be north of 100 gals, and that
> I'm likely to want to do, say, a 25% weekly water change (25 gals)
> this leaves me in what at first seems like a pickle. Namely, the
> pickle is not having enough water to complete the change.
>
> So, the first thing that popped into my head is to just do maybe 3
> smaller water changes during the week. The amount to be so changed
> will be such as to equal, after the third change at week's end, the
> net effect of a 25% water change.
>
> My calculation for a 100-gal tank is that you change about 9.14 gals
> three times. This is, remember, an amount less than the 10gals I'll
> be able to make in a day. The math is:
>
> (v) = t - (t * ((f)^(1/n)))
> where:
> v = volume to be changed
> t = tank volume
> f = fraction of original water to remain
> n = number of water changes
> Here 9.14 = 100 - (100 * ((0.75)^(1/3))).
>
> Hrm, interesting, I thought. You see where this is going, don't you?
> :)
>
> As above, I said "let n=168*60", the number of minutes in a week. The
> result is something like 11 ml per minute.
>
> I'll likely be running a wet/dry filter and CO2 injection. Given the
> above, I plan simply to withdraw ~4 gals of water from the system in
> the morning (the w/d will, I hope, continue to run in a system down 4
> gals) and then start dosing with the pre-made water-change water at
> 11ml/minute. I'm guessing a good CO2 reactor will be able roughly to
> keep up with the addition of water at this rate, and that as a result
> the [CO2] and pH swing experienced in the tank will be less than if I
> were to dump 25 gals of conditioned (but not CO2-injected) change
> water. There won't be stress on the heater, since the water will be
> preheated.
>
> An additional advantage, I think, is that I can put a daily dose of
> fertilizer in with the ~4gal of daily water change water, thereby
> giving my plants a nice even feed throughout the day/week.
>
> On paper this idea seems like a real winner. Still, I haven't really
> read about anyone doing it. This makes me think there's a hidden
> gotcha somewhere, but I'll be darned if I can see what it is.
>
> What say you?
>
> --Trapper

[Michi Henning]

"Brian S." > wrote in message
news:s1fed.303213$3l3.18271@attbi_s03...
>
> In addition to that, you may run into a problem with your tank actually
> flooding over if you add more than the tank can handle.

An easy way to prevent overflow is to use a continuous siphon.
It's foolproof and doesn't require any drilling:

http://www.triodia.com/staff/michi/aquatic/overflow.jpg

Cheers,

Michi.

--
Michi Henning Ph: +61 4 1118-2700
ZeroC, Inc. http://www.zeroc.com

[Trapper]

"Brian S." > wrote in message news:<s1fed.303213$3l3.18271@attbi_s03>...

[Brian top-posted, and I paste his reply *below* mine, where it
belongs]

> "Trapper" > wrote in message
> om...
> > Howdy folks,
> >
> > [I will have to keep a mix of the water-change water
> > brewing in advance.]
> >
> > Logistically, I can't see keeping more than about 10 gals of water
> > change water on hand pre-conditioning etc.
> >
> > [***] Namely, the pickle is not having enough conditioned water to
> > complete [changes > 10 gals].
> >
> > [calculation for vol to be changed 3x to equal 1 25% change]
> >
> > (v) = t - (t * ((f)^(1/n)))
> > where:
> > v = volume to be changed
> > t = tank volume
> > f = fraction of original water to remain
> > n = number of water changes
> > Here 9.14 = 100 - (100 * ((0.75)^(1/3))).
> >
> > Hrm, interesting, I thought. You see where this is going, don't you?
> > :)
> >
> > As above, I said "let n=168*60", the number of minutes in a week. The
> > result is something like 11 ml per minute.
> >
> > I'll likely be running a wet/dry filter and CO2 injection. Given the
> > above, I plan simply to withdraw ~4 gals of water from the system in
> > the morning (the w/d will, I hope, continue to run in a system down 4
> > gals) and then start dosing with the pre-made water-change water at
> > 11ml/minute. I'm guessing a good CO2 reactor will be able roughly to
> > keep up with the addition of water at this rate, and that as a result
> > the [CO2] and pH swing experienced in the tank will be less than if I
> > were to dump 25 gals of conditioned (but not CO2-injected) change
> > water. There won't be stress on the heater, since the water will be
> > preheated.
> >
> > An additional advantage, I think, is that I can put a daily dose of
> > fertilizer in with the ~4gal of daily water change water, thereby
> > giving my plants a nice even feed throughout the day/week.
> >
> > On paper this idea seems like a real winner. Still, I haven't really
> > read about anyone doing it. This makes me think there's a hidden
> > gotcha somewhere, but I'll be darned if I can see what it is.
> >
> > What say you?
> >
> > --Trapper


> That sure seems like a lot of work and figuring for easy water changes.

The math took about one minute.

And while it's true that this is more work than a simple water change,
I think there are stability benefits worth the effort. It was to
hidden biological detriments of this approach, not to concerns of tank
overflow, that my post was ultimately directed.


> [I] understand that you want to do it [slowly] so you won't bother the
> PH, but if you are talking about 10% water changes three times a week, I don't
> see any harm in just siphoning it out and then dumping 10 gallons in.

Agreed. This is the standard practice. We all know from long
experience that our plants/fish seem not to mind the change. My whole
post is premised on the idea of making deviations in water chemistry
as slight and slow as possible, while still achieving desired overall
weekly water turnover.

Let's say my pre-conditioned waterchange water is 3ppm in dissolved
CO2. And let's say my tank water is 18ppm in dissolved CO2. If I
were to add 10 gal of preconditioned water to 90 gals of such tank
water, my pH/KH/CO2 chart tells me I can expect an immediate
short-term pH swing of about 0.05 pH units. Since pH controllers
reputedly keep your pH +/- 0.2ish units, there's no way I can say that
such variations wouldn't already be happening.

There's a distinction in that, though. Variability due to the pH/CO2
controller's precision, and due to other intangibles, I cannot really
control. Variability due to the way I change water I *can* control.

> If you are going to add 11 mL a minute, you are going to need some fancy
> equipment that will measure this.

Airline hose. Valve. Gravity. Wris****ch. Measuring vessel. :)

If I meter in my ~4 gallons in 22 hours or 24, it's probably not a big
deal. Tinkering with a simple gravity doser will be part of the fun,
though. Even if I get it totally cocked up in testing, I'm still only
talking about adding ~4 gallons.

> In addition to that, you may run into a problem with your tank actually
> flooding over if you add more than the tank can handle.

Perhaps I didn't write it as clearly as I could have above, but my
plan is to add slowly only that amount of water which I first remove
from the tank. In this way, the worst-case scenario is either fill
failure (in which case I come home at night and find I have to add 4
gals manually) or fill insanity (in which case the 4 gals will be
added rapidly anyhow).

I'm not contemplating doing anything that can possibly overflow the
tank.

>
> Brian S.

--Trapper

[Billy]

"Trapper" > wrote in message
om...
| "Brian S." > wrote in message
news:<s1fed.303213$3l3.18271@attbi_s03>...
|
| [Brian top-posted, and I paste his reply *below* mine, where it
| belongs]
|

This is an aquaria NG. Please don't start that crap again. If
top-posting really bothers you that much, don't reply, but let's try
to avoid the spite.


---
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[Mr Happy]

If the Enterprise needs a Science Officer you might get the job!

sounds like a lot of effort for a job that will only take a few
minutes at worst

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[NetMax]

"Trapper" > wrote in message
om...
> Howdy folks,
>
> I'm going to be setting up a biggish tank soon, and I'm going to have
> to perform water changes with water deviant in several important
> respects from tapwater. Thus, I will have to keep a mix of the stuff
> brewing in advance.
>
> Logistically, I can't see keeping more than about 10 gals of water
> change water on hand pre-conditioning etc.
>
> Given the size of my tank will likely be north of 100 gals, and that
> I'm likely to want to do, say, a 25% weekly water change (25 gals)
> this leaves me in what at first seems like a pickle. Namely, the
> pickle is not having enough water to complete the change.
>
> So, the first thing that popped into my head is to just do maybe 3
> smaller water changes during the week. The amount to be so changed
> will be such as to equal, after the third change at week's end, the
> net effect of a 25% water change.
>
> My calculation for a 100-gal tank is that you change about 9.14 gals
> three times. This is, remember, an amount less than the 10gals I'll
> be able to make in a day. The math is:

<snipped math>

> An additional advantage, I think, is that I can put a daily dose of
> fertilizer in with the ~4gal of daily water change water, thereby
> giving my plants a nice even feed throughout the day/week.
>
> On paper this idea seems like a real winner. Still, I haven't really
> read about anyone doing it. This makes me think there's a hidden
> gotcha somewhere, but I'll be darned if I can see what it is.
>
> What say you?
>
> --Trapper

If your change water is within a change-range of your source water, I
would subtract/add the required water without concern. Change-range
depends on various parameters, so for 25% on a 100g, I'd estimate your
change range to be about 1.0pH, 10dgH, 10ppm NO3 and 5C. This change
range should be reduced for new fish, juveniles, sick or otherwise
stressed fish. The change range could be increased for the opposite,
healthy, large, acclimated etc. In their natural ambient, fish move
through stratified layers of salinity, hardness and temperature, so some
variation in natural parameters is not a concern to healthy fish. Fish
do NOT tolerate rapid changes of natural parameters, and they react
differently to variations in non-natural parameters (ie: nitrates), so
ymmv.

Assuming your water change idea still has application, then *I* don't see
any biological detriments (though the water removed should come from the
lower portion of the tank and you need to have a system to remove solid
waste accumulation), nor do I see significant overflow exposure (assumes
you are home daily, or your 4g system is not 100% automated and is
manually reset ;~).

For these types of systems, I prefer to calculate it to drops/min, and
make the automatic water changer into a continuous drip design. A
drilled overflow into the drain and a secondary overflow for failure
control (if you are in a water damage susceptible environment or are away
for periods of time). This allows your system to wander up & down (with
municipal pressure) and be somewhat self-adjusting. Metering water in to
match water removed is a PITA to automate reliably (ie: failure-prone
corroding water level solenoids). The predominant failure mode on
continuous drip systems is a gradual reduction in supply, which is easy
to compensate and adjust with time, and has low worst-case failure
consequences. Also, you can still meter your PMDD independently.

caution: the aquaria ng's tolerance for posting styles does not naturally
extend to poster intolerances of posting styles ;~)
--
www.NetMax.tk

[Anoif]

Well, if you are that obsessive, go ahead, but you are making a ton of
extra work for yourself, and the fish won't care either way...
__________________________________________________
Posted via FishGeeks - http://Aquaria.info

[Trapper]

(Anoif) wrote in message >...
> Well, if you are that obsessive, go ahead, but you are making a ton of
> extra work for yourself, and the fish won't care either way...

Yes, I am that obsessive. :-D I'd like not only for the fish not to
care, but for them not to notice.

And now, even better (worse?) my hardware is starting to arrive,
muahahaaa.

--Trapper

[Nikki Casali]

Trapper wrote:
> (Anoif) wrote in message >...
>
>>Well, if you are that obsessive, go ahead, but you are making a ton of
>>extra work for yourself, and the fish won't care either way...
>
>
> Yes, I am that obsessive. :-D I'd like not only for the fish not to
> care, but for them not to notice.
>
> And now, even better (worse?) my hardware is starting to arrive,
> muahahaaa.
>

There's nothing better than a good old benign obsession now and then.
Sometimes, not so much necessity, but obsession can often be the mother
of invention.

Yes, go for it!

[Bernie]

We use a constant (24/7) turnover of new water coming in vs old water
overflowing out through our pre-drilled tanks (hoses lead to drains
which feed into a master storm drain). The input flow rate is
controlled (gauged) to prevent drastic temp/pH fluctuations.
Fish do exceptionally well once you have fixed the flow rate to
maintain the stability. It eliminates much of the maintenance
involved with frequent manual
water changes, and virtually eliminates any concern over ammonia or
nitrite buildups.
We use this method in two of our largest store display setups of 100
tanks each
(over 2,500 gals each).

Bernie
__________________________________________________
Posted via FishGeeks - http://Aquaria.info