In what way do they benefit from water changes?

Visual appearance (polyp extension) and growth.

The cyclic change in the visual appearance of your coral is due to your
cyclic water changing. Your bacteria cell count roughly stays the same if
you are changing the same amount of water with each change ('steady state').
Your water changes are a cyclic event (if you are doing them on a regular
basis). Before and after a water change your existing bacteria are
metabolizing the aforementioned nutrients. Just before a water change your
bacteria are saturated with nutrients (they have enough to go around, all
are happy). They are able to metabolize the majority of the nutrients just
before your water change. Your nutrients will reach a peak concentration
just before your next water change (I am not saying they reach a high level,
just a peak concentration). If you didn't do water changes your bacteria
would proliferate and 'catch up' with the excess nutrients.

Your coral probably 'perk up' after a water change because of these cyclic
changes in nutrient (bacterial) concentrations.

Because I do NOT do water changes, my bacterial nutrient concentration
levels are NOT cyclic. My bacteria nutrients have reached a 'steady state'
level in response to my current bioload. My coral will always appear
'perked up'. There is NO cyclic event for me with NO water changes.

Many reef aquarists report that they can visually observe a slow decline
of
the daylight polyp extension of their soft and stony corals (in the
absense
of water changes), and also that there is an immediate positive response
in
the day or so after a water change.

See above. Plus: If they would let their bacteria proliferate to a point
where the bacteria can handle the present bioload with no water changes,
BEFORE adding the coral, there would be no "slow decline".

I agree that it is unclear how this relates to ammonia or other nitrogen
levels in those same tanks. But the coral response to water changes is an
obvious and very common effect.

See above.

Increase your bioload and your bacteria cell count goes up (there is a
ceiling for this, which is why aquariums can be over stocked).
Why is this so difficult to understand? My bioload is not relevant! As
you
increase your bioload your bacteria proliferate!

How can you not see it? You've answered your own question yourself.

??

To be more precise, the reason we want to know your bioload is to estimate
what the overstocking level IS for your recommended no-water-change
approach.

Telling you what my bioload is will not allow you to make this "estimation".
Please elaborate.

Surely even you can understand that it might be possible that a reef tank
with
regular water changes is able to successfully support a HIGHER bioload
than
your suggested strategy of no water changes.

Sure, you could probably get away with 'over stocking' an aquarium if you
did more frequent water changes.
I have no intention of 'over stocking' my aquarium.

The only way to resolve this is to know what, precisely, your bioload is.

How would this resolve it?

Yes we know you claim to be successful with no water changes. Yes we know
you measure your nitrogen compounds. Yes we know your bioload is below
your
overstocking level for your tank.

But we don't know WHAT your overstocking level is! Nor whether it is
significantly less than the stocking level in typical successful reef
tanks
(that do use water changes).

What is the stocking level in a typical successful aquarium?

Does that explain it? In any case, whether you understand our reasons or
not,
why are you so reluctant to just answer the simple question? What,
exactly,
is your bioload?

It is NOT relevant.

Because it doesn't matter. Your bacteria will proliferate in response to
increased bioload (within reason, ANY tank can be over stocked).

And the critical question is that perhaps your no-water-change tank can be
overstocked far earlier than a similar tank that does do regular water
changes.

Sure, you could probably get away with 'over stocking' an aquarium if you
did more frequent water changes.
I have no intention of 'over stocking' my aquarium.

What do you think will happen to your helpful little bacteria if you
removed
the majority of there food with each water change? Do you think they
will:
A) Starve and start to dye off. Cell count drops
B) Continue to be happy.

Their food comes from the waste products of the fish (and uneaten
decomposing
fish food). Those fish are still there, constantly spewing out waste
material. The new water will quickly fill up with bacteria food again,
and
there will be minimal impact on the bacterial populations.

Half correct. Your fish will roughly produce waste (with same bioload and
same feeding schedule) at a constant rate.
See above regarding 'steady state' bacteria levels. If you still have
questions let me know.


What do you think will happen to your bacteria if you took away the
majority of there "food: NH3/NH4, NO2-, NO3-" with each water change?

(Almost) nothing.

Wrong! If you regularly change X gallons of water you will reach a 'steady
state' bacterial cell count level. They will proliferate OR dye in
response to food supply. They will reach a population based on their food
supply levels. If you suddenly change X+10 gallons, you are removing
nutrients that they were accustomed to receiving. They will respond by
dyeing off to a population level that is in line with their 'new' food
supply levels. If you suddenly start changing X-10 gallons they will slowly
proliferate in response to the excess nutrients available to them (to a
point limited by substrate).

I hope this helps.



All that food will come back into the new water in minimal time.

-- Don
__________________________________________________ _____________________________
Don Geddis
http://reef.geddis.org/
A celibate clergy is an especially good idea, because it tends to suppress
any
hereditary propensity toward fanaticism. -- Carl Sagan, "Contact"