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Re: RO against Seradest (+ anybody from Belgium ?)



From: "Szalies Jean-Marc"
Sent: Friday, August 11, 2000 4:37 AM

> >Two questions:
> >1. How quickly are these concentration shifts taking place?...
>
> One afternoon (about 100 liters tanks (1m*0.5, 30cm height),
> about 35l water changed) [JMS]

The change in osmotic differential may be a little quick for the Rams. Try
two 20-liter changes across two afternoons. Add the softer water gradually,
as with an air line siphon to drain the fresh water into the tank. It'll
soften the blow a little.

> >2. What's happening in your tank as far as _alkalinity and pH_ ?...
>
> pH was about 7.2
> first dilution, about 6.8
> peat filtration gradually down to 6.6
> second dilution to about 6.5
> (this with precise pH paper)
> I think my test is total hardness, I shall also check for
> carbonated hardness as I have found a test in the lab ;)

The first change creates a 0.4 point pH shift, while the second only 0.1.
The implication here is that between the first change and the peat
filtration, the greatest part of your alkalinity has been "toasted". So your
carbonate hardness isn't nearly as great as the general hardness.

I would monitor what's occurring in the tank _as you make the change_ and
for a couple of hours afterward just to keep an eye on the stability. Even
at it's greatest, though, the first 0.4 point pH shift isn't enough to
greatly stress the fish in and of itself, but if the water "yo-yo's" for a
little bit while seeking a new equilibrium it could definitely upset the
fish.

As you approach the mid-6s in pH the alkalinity is pretty well exhausted,
making the time scale of any fluctuations a little more "immediate".

> I started in another tank peat filtration at the same time
> without any problem for the cacatouides living therein
> (but didn't dilute further than 12 up to now).[JMS]

Peat by itself tends to make fairly gradual changes, with the greatest
effects within the first two days of use. The cockatoos had the advantage of
this gradual shift without the added effect of the additional hardness
reduction happening simultaneously.

In the long run, once your pH drops to the sub-neutral range, it's a good
idea to keep the peat running. The humic acids that are normally released
start replacing the carbonates as the primary buffering agent. But they're
weak agents, easily overcome by processes like nitrification, so it's
important to refresh the water often through change-outs. To _that_ end,
it's also more effective to also have your fresh change water peat filtered
in a reservoir outside of the tank. That way, you aren't removing the
nitrogen compounds and having to sit back and wait for them to be replaced
by a build-up of humics.

One drawback to this is the use of peat from standard aquarium sources like
Fluval. Once processed for the filter for consistent texture, etc., there
are a great deal of useful humics removed. Why? Because a lot of people that
want the chemical effects of peat don't like the accompanying "visual"
effect of staining the water. Little do they know...

You're much better off, especially when treating change water reservoirs,
using a good, clean source of garden peat to obtain a fuller complement of
the humics. Barring the availability of clean garden peat (a distinct
possibility in Europe), you could soak things like Oak leaves and bark in
the reservoir to achieve pretty much the same effect.

If you're worried about using the peat itself, take a look at
http://www.mindspring.com/~nestor10/trials/peat_trials.htm . It's a page I
threw on the site a little over a year ago to outline an intended study
project in the hopes of better illustrating the "generalities" of peat
filtration. Unfortunately, my private life hasn't yet afforded the
opportunity for the full run...

-Y-




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