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RE: Aquatic Plants Digest V6 #137


> Date: Mon, 28 Apr 2003 00:50:31 -0400
> From: Cheryl Trine <ctrine at andrews_edu>
> Subject: Flourite as a substrate for Corydoras catfish?
> All the advice I have read about keeping Cory cats indicates that the
> gravel substrate should be rounded so that they won't wear their
> down to nubs.  After I washed my flourite with bare hands, they felt
> rather rough and scraped up, so I am wondering if this is an
> substrate for a planted tank with cory catfish.
> If flourite shouldn't be used, what would be a good alternative?
> I cover the flourite with about an inch of rounded gravel or sand?
> Would this just get mixed when vacuuming the surface, and bring the
> flourite to the top?

Someone else will have to answer your question about any potential
damage to the barbels on Corys.  I do not know and will not spread
something I am not sure of.  However I have had some recent experience
with mixing gravels.  I have been trying several with different sizes
and shapes.

I wanted to see how some different substrates I was considering would
look under the lighting in the tank and finally came down to three I
wanted to try.  At first I put a couple of scoops of each in adjacent
areas in the tank.  I carefully tried to place them so that from
different vantage points (with the rocks and plants and all) it would
appear that only one of them was in the tank.  The first few hours were
a good representation and the family quickly picked their favorite look.
I was stunned at how quickly things changed.

This tank had an army of MTS and they made quick work of mixing the
original gravel below with the new substrates I had just introduced.
Within four hours there was a noticeable portion of the surface covered
by the old gravel.  There was so much original mixed in that you could
no longer get a good idea of how the different colors looked.  I did
this in the late afternoon/early evening.  By the next morning the
proportions had swapped - now there was only a noticeable portion of the
new stuff as it had been replaced by the old.  About 24 hours later you
could just barely tell there was some there.  For the most part, at this
point the new stuff was only visible where the substrate met the glass.
Over the next few days I watched the new stuff, in all three cases,
gradually 'sink' towards the bottom.  It almost seemed like the MTS's
were attracted to it and determined to move it down.  Looking at the
edge of the substrate through the glass, by the end of the second day
the new stuff looked like a subsurface sedimentary formation (like the
layers on the Grand Canyon or an outcropping cut in a hill for a
highway).  I knew this would happen but I was truly amazed by how fast
it did.  I had no idea the substrate was that 'alive'.

Although I had carefully placed the new material in specific areas there
was also horizontal migration on the surface.  All of the areas mixed
with the others.  Though some were quicker than the others and spread
farther, the result was the same in each case - everything mixed to some

Color wise I had pretty much narrowed it down to two and a week or so
later I tried the one everyone liked best in a new setup.  It was all
black.  After a few days I was not certain (actually it was again a
family consensus) that the first choice looked as good as we thought.  I
shifted some of it from one end to the other, in the process raising the
depth to about 3+" (where I wanted it anyway), and added a large enough
portion of the other cover half the tank and have a 3-4" depth at the
end I added on to.  It was a medium brown/gray mix with a few pieces of
red stuff.  There was no doubt which was where.  It has been a couple of
weeks and I have decided on the solution:  I will use some of both.  The
surface of the tank is pretty well mixed - actually at least some of it
(see below).  The two samples look very good together and the plants
seem to be doing fine.  Like you I had kind of shied away from the
Flourite because it was very course on my hands as well.  However, I
will add that I have seen several postings here by some of the most
experienced and respected on the APD list who swear by the stuff.  I am
sure that there are more than a few Corys in their tanks.

I would like to add one odd observation that I have trouble
rationalizing.  I put a small grade in the tank from right to left so
that whatever stuff accumulated on the bottom would gradually work
towards the filter pickup.  I would have expected the stuff at the
higher level (brown/gray substrate) would move towards the filter pickup
until the substrate was fairly level.  I guessed I would end up with
mostly brown gray stuff at the right end and a good mix on the left near
the filter.  I also anticipated the big stuff at the top with the
smaller ones settling to the bottom.  I have been surprised again.  The
black stuff has moved 'uphill' and mixed rather nicely with the
brown/gray.  There is no area where I put the brown/gray that is not
well mixed with black.  I have done nothing to encourage it but it looks
like I mixed them together before putting them in the tank.  Some of the
brown/gray has indeed moved 'downhill' but there are still some large
areas of pure black at the shallow end, and I would say that at least
40-50% of the all black area is still all black.  This is particularly
true around the filter inlet.  Strange.

BTW, the first setup mentioned was infested with MTS and some other
small snail.  I tried to get things moved over without transferring the
snails because they had gotten way out of hand.  No such luck.  I did
not reuse any gravel (I know Tom advocates saving some mulm but I did
not want the snail hoards) and washed the plants but apparently not well
enough.  I guess I got some eggs because I have a bunch of the unknown
(to me anyway) type and recently saw one MTS (yes, I know there must be
more).  But the snail population has just now gotten to a really
noticeable level.  While most of the substrate migration was going on
you could only find a couple of snails and all of them were pretty

Hope this helps.


> Thanks for any advice.
> Cheri
> ------------------------------