How Much "medicine" Is Too Much

[BaylorPerez]

Ah i see, well i wont add it to the tank itself

 

[Byron]

I earlier mentioned aloe vera and its dangers, so in fairness I thought it might be instructive for other members to see some data.  This excerpt is from a study looking into polymers in conditioners, used to prevent damage to the slime coat of fish in netting, handling, etc., and it has a good paragraph on aloe vera:
 
Contents of water conditioners
 
Many water conditioners are commercially available,
but some are formulated only to dechlorinate water
and/or bind heavy metals. These conditioners use
dechlorinating agents such as sodium thiosulfate and
ascorbic acid, chelating (metal binding) agents such as
ethylenedianinetetra acetic acid (EDTA), and buffering
agents such as tris (hydroxymethyl) aminomethane
that restore acid–base balance. Water additives
that form a protective ‘‘slime layer’’ will contain a
polymer (often PVP or carboxymethyl cellulose
[CMC]) or colloid (Table 2). Some additives contain
aloe extract from leaves of the Aloe vera plant.
Manufacturers of these products claim that the Aloe
vera extract promotes healing of damaged tissue. One
potential drawback to water additives that contain
Aloe vera extract or CMC is the addition of organic
waste load that can reduce the water quality and
oxygen levels in a closed system. This may not be
an issue, depending on the density of fish, length of
time fish are held, and oxygen content of the water.
However, the effects of these substances on gill tissue
are unclear. Taiwo et al. (2005) tested the survival and
behavior of tilapia (Oreochromis niloticus) exposed to
different concentrations of aqueous extract of A. vera
for up to 96 h. One hundred percent of tilapia exposed
to 50 ppm A. vera died within the duration of the
experiment. Fish used in this experiment exhibited
severe depigmentation and destruction of organs
(including gills). The evidence of the toxic effects of
A. vera on fish solidifies the need to empirically test
water conditioners, and their chemical components,
for potential negative effects on fish.
 
You can see the entire paper (it is not very long) here:
http/jsats.pnnl.gov/Publications/Peer/2011/Harnish%20et%20al%202011_Water%20Conditioners.pdf