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Fish that Damage Plants


  1. Aquatic Plants Digest V1 #176
    by "Thomas Narten" <narten-at-VNET.IBM.COM> (Wed, 12 Jul 95)
  2. clown loach, blue-green and tank cycle
    by KB Koh <> (Fri, 14 Jul 95)
  3. bad fish (particularly Clown Loaches)
    by David Randall <> (13 Jul 95)
  4. Eureka! (I think)
    by "Roger S. Miller" <rgrmill/> (Wed, 24 May 2000)

Aquatic Plants Digest V1 #176

by "Thomas Narten" <narten-at-VNET.IBM.COM>
Date: Wed, 12 Jul 95

>For instance, I had angelfish who destroyed my giant Hygro by
>nipping off new shoots, and Congo Tetras who desctroyed my Anubias by nipping
>off new shoots, but I've never heard confirmation of this from anyone

Consider it confirmed. I recently got rid of 4 large angels that
effectively destroyed my Giant Hygro, H. polysperma and mayaca.  These
are the first angels I've had that have been serious  plant eaters,
that is, ravenous enough to destroy the plant. Mostly, they just nip
the leaves enough, but they grow back faster.

Oh, the angels loved duckweed as well.


clown loach, blue-green and tank cycle

by KB Koh <>
Date: Fri, 14 Jul 95

>From: David Randall <>
> Subject: Re: bad fish (particularly Clown Loaches)

> In general, I have had no trouble with Clown Loaches in my planted tanks
>except for one extremely aggravating exception... Whenever my Anubias flower,
>they _immediately_ attack the flower as soon as it is open and devour it!.

When I first bought the clown loaches, they did not attack any plants in the 
first two week. It then started to attack new tender leaves of E. Osiris and 
broken its main vein (the one continue from petiole). They did not attack 
anything else until I brought in E.Opacus(?), E.Quadricostatus and a small red 
lettuce-like plant. They punch holes all over E.Opacus leaves and almost 
completely destroyed the red plant. I get rid of the clown before it further 
damage my Quadricostatus (a plant that I had been searching for 2 months!) BTW, 
these clowns use their mouth to punch those holes.

bad fish (particularly Clown Loaches)

by David Randall <>
Date: 13 Jul 95

 In general, I have had no trouble with Clown Loaches in my planted tanks
except for one extremely aggravating exception... Whenever my Anubias flower,
they _immediately_ attack the flower as soon as it is open and devour it!.
They seem to find it irresistible.  They attack like sharks in a feeding

 Another interesting observation I've made with plant eating fish is that in
my "low tech" tanks with slower growth, I never had any trouble with Rosy
Barbs eating enough plants to be a problem.  When I first added CO2 and
brighter lighting to my tanks, the Rosy Barbs decimated the H. difformis and
several other fast growing soft leaved plants.
 My guess is that the soft new growth was "tastier".

 Finally, I have a large pair of Pearl Gouramis in one of my tanks.  They have
been there for several years, and have been very well behaved.  Although they
do occassionally nibble plants, they have never caused enough damage that the
plants couldn't out grow it.  Last year I go some Rotala wallachii. (which, of
course I had been looking for for some time :-() They left the stand alone for
quite some time, and it grew large and luxuriant.  Then one day, for no
obvious reason, they took a liking to it.  In 24 hours, they reduced it to
stubble.  To save it from total destruction, I removed it to another tank at
that point.

  E-mail from: Karen Randall, 13-Jul-1995

Eureka! (I think)

by "Roger S. Miller" <rgrmill/>
Date: Wed, 24 May 2000


I have repeatedly posted to this list about a hard-to-solve problem in one
of my tanks.  Briefly, lesions develop on the leaves of C. wendtii, C.
cordata and Hygrophilla corymbosa, usually near the center of the leaves
and usually about the time that new leaves are reaching full development.  
Over time the lesions become more common and the existing lesions become
enlarged.  Eventually the leaves take on a corroded look and die.

Following is a rather long narrative leading up to the conclusion that the
problem was caused by my little plecos.

Several years ago I had these symptoms and a few others on a slightly
longer list of plants and I was able to reduce those problems with a
change in lighting and a small dose of magnesium and potassium.  It's long
been my expectation that the remaining problems were also caused by a
nutrient deficiency - probably potassium, and probably caused by a severe
imbalance between sodium and potassium in my tap water.  I dosed potassium
in the water up to 20 mg/l and I added additional potassium with
fertilizer sticks, roots tabs and other commercial preparations without
any observable effect

The symptoms are limited to plants in only one of my tanks, so I needed a
cause that was unique to that tank.  I use the same water in all my tanks
so nothing directly related to the water is unique to the problem tank.  
As a result I looked into indirect causes and also thought that the
problem might be caused by a toxicity to something in the tank.

Last year I posted to the list, asking about toxicity to various plastic
parts and Justin Collins replied that some of his friends had problems
when the suction cups on Rio pumps dissolved (odd behavior for a bit of
platic). I filed that idea away until a couple months ago when I checked
the suction cups on my Rio powerhead and found them severely corroded.

I replaced the Rio and waited to see what happened.  The tank had a green
water bloom almost immediately.  When the green water cleared up I noticed
that both the C. wendtii and C. cordata had taller, healthy looking new
leaves.  I hoped then that I finally found the problem, but lesions
appeared on the tall new leaves just a couple days later.

Then last week I posted about pleco damage on an Echinodorus "Rose'" in
the same tank.  I started giving the little dwarf clown pleco's parboiled
zucchini (something that in the past I did only occasionally) to keep them
off the E. "Rose'".  Sunday in my weekly cleaning and pruning I noticed
not only that there was no new damage to the leaves on the E. "Rose'", but
that new leaves on the C. wendtii and C. cordata were completely
unblemished.  I removed most of the older, damaged leaves to make any
changes more readily observable.  Happily, all of the new leaves still
remain completely undamaged.

So now, after at least 5 years of trying to find the cause of this
problem, I think I have a culprit -- the cute little clown plecos that
have lived in that tank now for 12 years.  What I think is odd is that
I've almost never seen the plecos on any of the plant leaves.  They're
usually gnawing away in and around the driftwood.  I see them on the
plants so rarely that I actually thought they had an aversion to the
plants.  Damage on the E. "Rose'" was recognizable pleco damage and the
first clue I had (OK, I'm slow) that the guys didn't find plants mostly

This seems to solve my problems in this tank with C. wendtii and C.
cordata.  The problem with H. corymbosa is very similar and I expect that
damage will disappear as the plants put on new leaves.  This probably also
explains very similar symptoms I had on Anubias barteri nana in this tank
several years ago.

The Rio suction cups didn't cause the lesions, but I wonder if they may
have released something as they dissolved that suppressed the growth of
some plants.  The C. wendtii and C. cordata changed their height
fairly abruptly when I took the Rio out.  Could the change in habit be
caused by a spring-time temperature increase of a few degrees?  Whatever
the cause, it looks like the suddenly-taller C. cordata are going to make
me redo my aquascape before I can photograph things for the AGA contest!

Roger Miller

in Albuquerque, where it's about as dry as you can imagine and no
significant rains can be expected for another month and a half.

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