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Re: low water-change setups

Carlos Munoz wrote:

> Who's had a successful long-term setup (approaching a year or more) with
> minimal and/or infrequent water changes (<10%/month or so on average). If
> you had one for less, what caused you to return to frequent water changes?

I've never done this intentionally (well, not since I was 14 or so,
anyway) but I was pretty much forced into it for a while by a combination
of young children, long work hours and frequent business travel.  I went
back to regular water changes when time allowed because I think its
all-around better husbandry.

> I'd like to know a little bit about your setups, the plants that do best
> in your setups, and compromises you had to make to make the tanks run
> smoothly.  Was there a breaking point when you had to do a large water
> change?  What was the top-off or water change rate?  Any fertilizers?
> What is your top-off water make-up? Any useful anecdotes?


I wasn't very good at keeping plants back then, mostly because the lights
were too dim.  There were crypts and anubias in the tanks, and they did
OK.  My water is very well buffered and I used tap water for makeup.  I
think that let me get away with the lack of maintenance.  The worst
problem was with recurring, large bluegreen algae infestations.

Monitor the alkalinity if you can - its a good early warning for an
impending pH drop.  It will probably drift either up or down, depending on
your tank water composition, evaporation rate, makeup water composition,
and feeding rate.

If it drifts up then you are probably safe from the worst problems.  At
least for a while.

If it moves down then you will want to do a water change or (short-term
solution) add some bicarb.  It seems that bacteria - even without a
biofilter - must metabolize a lot of the things that might build up over
time, but bacteria are suppressed below neutral pH (fungi are stimulated),
and the amount of suppression increases as the pH drops (hence, pickling
works, vinegar is a preservative and acid vegetables are easy to can).
Unfortunately, if the pH does drop substantially then it will probably do
so suddenly, and your tank might go from apparently healthy to dead over
the course of a couple days.

Regardless of whether the alkalinity moves up or down, you will see a salt
buildup over time.  If you have very fresh water to start with, and keep
feedings light, then it will take a long time for that to be a problem,
but because of the feeding it will happen eventually anyway.

If you use distilled or RO water for makeup then you may exacerbate the
alkalinity drop, but you will help slow down the salt buildup.

Roger Miller