water evaporation and topping off

[Ron H]

Is it ok, that my aquarium looses about a gallon of water every day or two
due to evaporation, and I just keep topping it off with RO water ( no Salt)
and keep
on doing so, and doing no real water changes?

Ron

[reefman MC]

As long as your salinity stay stable you should be fine.


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[peobrien]

Monthly water changes are a must.

topping off your tank with plain RO water is fine. The salt does not
evaporate like the water.

"Ron H" > wrote in message
...
> Is it ok, that my aquarium looses about a gallon of water every day or two
> due to evaporation, and I just keep topping it off with RO water ( no
Salt)
> and keep
> on doing so, and doing no real water changes?
>
> Ron
>
>
>
>

[Ross Bagley]

"Ron H" > writes:

> Is it ok, that my aquarium looses about a gallon of water every day
> or two due to evaporation, and I just keep topping it off with RO
> water ( no Salt) and keep on doing so,

Evaporation should always be replaced with the purest fresh water you can
get your hands on. You're doing this part exactly right.

> and doing no real water changes?

You should probably do periodic water changes in addition to your
fresh water top-off. This can be a pain and many aquarists are able
to "get away" without water changes, but your fish and animals will be
happier in the long term if you are regularly diluting the toxins that
you don't have test kits for and are replenishing the depleted trace
minerals that you also don't have test kits for.

When doing a water change, mix the water at least 24 hours in advance.
There are several hydration reactions that need to run to completion.
There are also several biotic processes that will isolate some of the
metallic ions that are needed in your aquarium, but are harmful in
their simple ionic form.

Regards,
Ross

-- Ross Bagley http://rossbagley.com/rba
"Security is mostly a superstition. It does not exist in nature...
Life is either a daring adventure or nothing." -- Helen Keller

[Aquatic-Care]

Ron,

Make sure you buffer the RO you are using to top off your system. RO water
is very acidic and will make your PH bottom out if not properly buffered. I
have had many people make this mistake. Just a little note.

aquacare




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[Ross Bagley]

"Aquatic-Care" > writes:

> Make sure you buffer the RO you are using to top off your system. RO
> water is very acidic and will make your PH bottom out if not
> properly buffered. I have had many people make this mistake. Just a
> little note.

I've heard that RO permeate can be slightly acidic (and is almost
always more acidic that the supply) because the most common RO
membranes have higher rejection rates of alkalide ions than they do of
acidic ions. There are more expensive "wide pH range" membranes and
higher rejection rate membranes which do a better job of rejecting the
acidic ions and tend to minimize the pH drop.

What I haven't heard before is that RO water is "very acidic". Is
there something you could point me to that I could read? A quick
google search yielded plenty of "slightly acidic" links but not
necessarily what you may be talking about.

Also, most aquarium feeds are RO/DI (like this guy's system). As long
as they're replaced before complete exhaustion, the deionization
stages will take care of *any* acidic ions left by the RO membrane.

Regards,
Ross

-- Ross Bagley http://rossbagley.com/rba
"Security is mostly a superstition. It does not exist in nature...
Life is either a daring adventure or nothing." -- Helen Keller

[Aquatic-Care]

Ross,

I don't have any reasearch that I can point out, but I will do some extra
testing on a few Ro/DI systems I have running to check the acid levels.
Every time I test them I notice an acid test in the low 6.0 range which is
Very acid compared to 8.0-8.3 in a salt tank. Even if the RO/DI units have
Neutral 7.0 water comming out and you continually add it to 8.0-8.3
eventually you will have a problem. I will admit there are alot of vaiables
(alkalinity, calcium and other inherent buffers) to take into consideration.

aquacare


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[Ross Bagley]

"Aquatic-Care" > writes:

> Ross,
>
> I don't have any reasearch that I can point out, but I will do some extra
> testing on a few Ro/DI systems I have running to check the acid levels.
> Every time I test them I notice an acid test in the low 6.0 range which is
> Very acid compared to 8.0-8.3 in a salt tank.

The thing is that if the 6.0pH is completely unbuffered HCl, that's a
10^-5 molar solution. Really, really weak acid. About a thousandth
as acidic as your stomach after a meal. As in that's an acid that
will be totally overwhelmed by the buffering capacity of NSW or the
typical tank water.

Now, making sure that your alk doesn't drop to zero is important, but
the few ions contributed by purified top-off water aren't even going
to scratch the buffering capacity of a sal****er tank over the course
of several years. Biological processes in the tank are going to have
a much bigger effect on your alkalinity than purified top-off water.

> Even if the RO/DI units have Neutral 7.0 water comming out and you
> continually add it to 8.0-8.3 eventually you will have a problem.

If pH7.0 water is continually evaporating from your tank and you
replace it with pH7.0 water, is there ever going to be an issue?

Another way to look at it is that pure water (pH7.0) doesn't
contribute any ions to your tank water. It's just diluting the tank
water. The evaporation from the can be thought of as a that doesn't
remove any ions but just concentrates the ones that are there. If the
rate of dilution equals the rate of concentration and the number of
ions in the volume of water remains the same over time... is there
ever going to be an issue?

As an aside, evaporation does remove ions from the tank, most
dramatically in the salt creep that slowly covers things in and near
the tank. If you keep track of your salinity over time, this won't
affect you either way.

> I will admit there are alot of vaiables (alkalinity, calcium and
> other inherent buffers) to take into consideration.

Yep. pH isn't enough to say if a solution will have any impact on
your tank water. Not all pH6.0 solutions will have the same impact on
tank water chemistry. What really matters are the populations of the
various ions in solution.

The effluent of a filter and the effluent of a calcium reactor may
both have a pH of 6.5. But the reactor effluent has hundreds of
thousands of times more ions in solution than the filter effluent and
as a result, a significantly larger impact on your tank's chemistry.

Regards,
Ross

-- Ross Bagley http://rossbagley.com/rba
"Security is mostly a superstition. It does not exist in nature...
Life is either a daring adventure or nothing." -- Helen Keller

[Aquatic-Care]

Ross,

Interesting explanation. I will agree that ALL tanks are different and could
have a potential problem. I just can't take the risk so I add some
buffer/alkalinity to all top off water just to make sure. Expecially if the
Alkalinity in the tank is running low.

Thanks for the explanation,

Aquacare

[Richard Reynolds]

ok living dangerously here


> Monthly water changes are a must.

NOT even!!!!

but if you had to ask the first question then maybe they are for you :D

--
Richard Reynolds