Are water changes always necessary?

"blank" <blank.DeleteThis@void.net> wrote in message
news:3fdaf338$0$1745$5a62ac22@freenews.iinet.net.au...
> Every friday after work I go through the 20% water changing ritual, and
> every friday I wonder if I should really be doing it. The reason is
that my
> tap water is about pH 8 (even after leaving it for 24 hours) but the
water I
> am siphoning out each week is pH 7.3. So here I am dumping 6 buckets
of
> good water and replacing it with higher pH water every week. I do my
water
> testing every thursday, and all the paramaters are A-OK, and remain the
same
> week after week. So wouldnt I be better off to leave the water alone
so
> long as the tests show I have no problem?

The fact that your tank runs at 7.3pH and your tap is 8.0pH is evidence
of the necessity of continuing your water change routine. This means
that after a water change, your tank is 7.44pH : 80%7.3 and 20%8.0
(5.84+1.6=7.44), or (8.0-7.3=0.7/5=0.14+7.3=7.44). In one week, your
environment lowers your pH by 0.14 which is not a lot by itself, but the
fact that it is consistent and probably occurring in a higher than
average kH (with a 8.0pH) is worrisome. I suspect that you have a
problem which is being masked by your kH and water changes. Probably
causes are excessive detritus in substrate, too high a fish-load and
overfeeding.

To simplify your question, if all the water parameters were the same
before & after a water change, then you can ask yourself if it's worth
it. The more dissimilar they are, they greater your need to do regular
water changes. Note that when I say 'all parameters are the same', I'm
including things which we have no test kits for (the water is not just
NH3/4, NO2, NO3, PO, gH, kH & pH, - there are many many other things
happening in there). This is why even when everything is running
tickityboo, small regular water changes are still recommended. JMO

NetMax
 >> Stay informed about: Are water changes always necessary? 

>>The fact that your tank runs at 7.3pH and your tap is 8.0pH is evidence
>>of the necessity of continuing your water change routine. This means
>>that after a water change, your tank is 7.44pH : 80%7.3 and 20%8.0
>>(5.84+1.6=7.44), or (8.0-7.3=0.7/5=0.14+7.3=7.44).

The pH is in log scale so I think the math is this:

+-- --+ +-- --+
| 7.3 | | 8.0
|
| 10 * 0.8 | + | 10 * 0.2 |
+-- --+ +-- --+
new pH = log
10

= 7.55

I think this is right but I could be wrong.

Jim
 >> Stay informed about: Are water changes always necessary? 

"james mitchell" <bogus DeleteThis @cfl.rr.com> wrote in message
news:GRKCb.54490$b01.1399177@twister.tampabay.rr.com...
> >>The fact that your tank runs at 7.3pH and your tap is 8.0pH is
evidence
> >>of the necessity of continuing your water change routine. This means
> >>that after a water change, your tank is 7.44pH : 80%7.3 and 20%8.0
> >>(5.84+1.6=7.44), or (8.0-7.3=0.7/5=0.14+7.3=7.44).
>
> The pH is in log scale so I think the math is this:
>
> +-- --+
--+
> | 7.3 | | 8.0
> |
> | 10 * 0.8 | + | 10 * 0.2 |
> +-- --+
--+
> new pH = log
> 10
>
> = 7.55
>
> I think this is right but I could be wrong.
>
> Jim

Thanks Jim, my bad.

NetMax
 >> Stay informed about: Are water changes always necessary? 

"NetMax" <computeralias.DeleteThis@hotmail.com> wrote in message
news:EjKCb.19515$aF2.2235398@news20.bellglobal.com...
>
> "blank" <blank.DeleteThis@void.net> wrote in message
> news:3fdaf338$0$1745$5a62ac22@freenews.iinet.net.au...
> > Every friday after work I go through the 20% water changing ritual, and
> > every friday I wonder if I should really be doing it. The reason is
> that my
> > tap water is about pH 8 (even after leaving it for 24 hours) but the
> water I
> > am siphoning out each week is pH 7.3. So here I am dumping 6 buckets
> of
> > good water and replacing it with higher pH water every week. I do my
> water
> > testing every thursday, and all the paramaters are A-OK, and remain the
> same
> > week after week. So wouldnt I be better off to leave the water alone
> so
> > long as the tests show I have no problem?
>
> The fact that your tank runs at 7.3pH and your tap is 8.0pH is evidence
> of the necessity of continuing your water change routine. This means
> that after a water change, your tank is 7.44pH : 80%7.3 and 20%8.0
> (5.84+1.6=7.44), or (8.0-7.3=0.7/5=0.14+7.3=7.44). In one week, your
> environment lowers your pH by 0.14 which is not a lot by itself, but the
> fact that it is consistent and probably occurring in a higher than
> average kH (with a 8.0pH) is worrisome. I suspect that you have a
> problem which is being masked by your kH and water changes. Probably
> causes are excessive detritus in substrate, too high a fish-load and
> overfeeding.
>
> To simplify your question, if all the water parameters were the same
> before & after a water change, then you can ask yourself if it's worth
> it. The more dissimilar they are, they greater your need to do regular
> water changes. Note that when I say 'all parameters are the same', I'm
> including things which we have no test kits for (the water is not just
> NH3/4, NO2, NO3, PO, gH, kH & pH, - there are many many other things
> happening in there). This is why even when everything is running
> tickityboo, small regular water changes are still recommended. JMO
>
> NetMax
>
OK, thanks for that advice. My main tank is, after 6 months, a
smooth-running machine, with no problems. The fish are happy, the plants
are happy. Perhaps I should use the gravel-vac, but Ive read that's not a
great idea with lots of plants. I have a good supply of plecos, loaches and
snails to keep the bottom clean. And occasionally I skip the morning feed,
which results in an afternoon feeding scene resembling the UN giving out
grain in Biafra. So I think the feeding level is OK. Also the water is
very clear, with minimal filtration. But I do have quite a few fish. So
that may be the cause.

Anyway, I will continue with the regular water changes. Thanks for your
help, I'v learned a lot from this group, especially from your contributions.
 >> Stay informed about: Are water changes always necessary? 

"james mitchell" <bogus RemoveThis @cfl.rr.com> wrote in message news:<GRKCb.54490$b01.1399177@twister.tampabay.rr.com>...
> >>The fact that your tank runs at 7.3pH and your tap is 8.0pH is evidence
> >>of the necessity of continuing your water change routine. This means
> >>that after a water change, your tank is 7.44pH : 80%7.3 and 20%8.0
> >>(5.84+1.6=7.44), or (8.0-7.3=0.7/5=0.14+7.3=7.44).
>
> The pH is in log scale so I think the math is this:
>
> +-- --+ +-- --+
> | 7.3 | | 8.0
> |
> | 10 * 0.8 | + | 10 * 0.2 |
> +-- --+ +-- --+
> new pH = log
> 10
>
> = 7.55
>
> I think this is right but I could be wrong.
>
> Jim

pH = -log[H+]

therefore:

[H+] = 10^(-pH)

On a simplistic level, assuming no difference in buffering capacity
between the tapwater and the tank (i.e. carbonate and phosphate
concentrations), changing 20% of the tank water (pH 7.3) with tap
water at pH 8.0 will alter pH by:

-log(0.2*(10^-8.0)+0.8*(10^-7.3))
=7.38
 >> Stay informed about: Are water changes always necessary? 

"David Lloyd" <david.lloyd RemoveThis @plants.ox.ac.uk> wrote in message
news:d9cc9d63.0312150352.129269c0@posting.google.com...
> > > On a simplistic level, assuming no difference in buffering capacity
> between the tapwater and the tank (i.e. carbonate and phosphate
> concentrations), changing 20% of the tank water (pH 7.3) with tap
> water at pH 8.0 will alter pH by:
>
> -log(0.2*(10^-8.0)+0.8*(10^-7.3))
> =7.38

Well there ya go !! I have never re-checked the pH shortly after the water
change. Will do that this week. So really I'm altering the pH of the whole
tank by 0.4 in about 10 minutes when I dump the six buckets of
(dechlorinated) tap water in. That probably explains why some of the fish
(eg the platies) look a bit stunned for a while after the change. It seems
like I need to add the water over a period of a couple of hours, one bucket
at at time, to allow the fish to adjust to the significant change. Thanks
for that David.
 >> Stay informed about: Are water changes always necessary? 

"blank" <blank.RemoveThis@void.net> wrote in message news:<3fdeea1b$0$1746$5a62ac22@freenews.iinet.net.au>...
> "David Lloyd" <david.lloyd.RemoveThis@plants.ox.ac.uk> wrote in message
> news:d9cc9d63.0312150352.129269c0@posting.google.com...
> > > > On a simplistic level, assuming no difference in buffering capacity
> > between the tapwater and the tank (i.e. carbonate and phosphate
> > concentrations), changing 20% of the tank water (pH 7.3) with tap
> > water at pH 8.0 will alter pH by:
> >
> > -log(0.2*(10^-8.0)+0.8*(10^-7.3))
> > =7.38
>
> Well there ya go !! I have never re-checked the pH shortly after the water
> change. Will do that this week. So really I'm altering the pH of the whole
> tank by 0.4 in about 10 minutes when I dump the six buckets of
> (dechlorinated) tap water in.

pH 7.3 to pH 7.38... You're only altering the tank pH by less than 0.1
of a pH unit. That's not huge.

> That probably explains why some of the fish
> (eg the platies) look a bit stunned for a while after the change. It seems
> like I need to add the water over a period of a couple of hours, one bucket
> at at time, to allow the fish to adjust to the significant change. Thanks
> for that David.

Is the water temperature in the buckets matched to that in the tank?
One of my early mistakes (not that long ago) was to put cold water in
the tank, which upset the inhabitants somewhat. Now I roughly match
the temperature by pouring some boiling water into the bucket before
changing the water. If it feels the same temperature it'll do. The
fish are happy.

How are you "dumping" the new water in? Siphoning the water in slowly
is the best bet. Pouring the bucket in will probably not be great for
them.
 >> Stay informed about: Are water changes always necessary?