One and Two
Jun. 02, 2000
In my more than eighteen years of keeping and breeding discus, the most
common cause of discus health problems is incorrect water conditions. Fish
keeping is not about fish. It is about water chemistry. If your water
chemistry skills are not honed to a sufficiently knowledgeable level then
you are doomed to failure. I will only discuss two elements of the large
family of water chemistry components here but I strongly advise that you
learn as much as you can about water chemistry in general. Your fish will
live a lot longer and you will enjoy your hobby a lot longer if you take
the time to do the research.
By far the two most deadly substances in discus water are ammonia
compounds and nitrite. Unfortunately, for a biological filtration system
to function correctly, both of these compounds must be present and must
also be chemically converted to the end product-nitrate-very fast and
efficiently by the filter.
For those of you that are new to discus keeping, your biological filter
is NOT the filter media but the nitrifying bacteria that inhabit the
media. I do not propose to describe how a biological filter works as there
are numerous articles available for that purpose. What I do want to
discuss is how to RECOGNISE and TREAT symptoms of ammonia and nitrite
poisoning. I will not bore you with the chemical reactions of both these
toxins as they are very complex.
Before we get involved in the fun part, let me just say this. Do not be
lulled into a false sense of security by believing that ammonia is
non-toxic in acidic water. Nothing could be further from the truth. I have
killed fish with ammonia in tanks with a pH as low as 3.8!!!. Also, the
higher the tank temperature the more toxic the ammonia. Scary stuff
If I was asked to pick the one task that was most neglected by fish
keepers I would have to say it is the simple job of testing their tap
water or whatever water source they use to change their tank water with
PRIOR to EVERY water change. With all the health-benefiting chemicals that
our water supply authorities dump in our tap water, the acid rain that we
collect and the contaminated river/lake/bore water that we use, I will
guarantee you that you will introduce certain death into your tanks if you
do not monitor it at every water change.
Chloramine-a combination of ammonia and chlorine-is routinely added to
our tap water. Good quality activated carbon and the correct water flow
rate over this carbon will eliminate chlorine but will NOT eliminate
ammonia. If you detect even the slightest amount of ammonia or nitrite in
your tap water you must use appropriate chemicals to detoxify them BEFORE
adding the water to your tanks. There are several products on the market
that will do this. The products that I use and recommend are Seachem's
"Prime" and "Safe". I could not keep my fish alive in
my tap water without these products as it is always loaded with one or
both toxins. Prime is most suitable as it does not need pre-mixing. I
strongly recommend that you keep some form of ammonia and nitrite detox on
hand for that emergency. Zeolite is very good for removing ammonia but it
won't take care of nitrite and it needs to be regenerated or thrown out
after it has adsorbed it's fill of ammonia. Please note that both ammonia
and nitrite will pass through reverse osmosis membranes and certain
deionising resins will remove ammonia.
The main source of ammonia in your tank will come from the fish's
gills-assuming you're not grossly overfeeding. If there is sufficient
ammonia in the tank, your fish will not be able to excrete ammonia through
their gills and will be poisoned-either very slowly or extremely fast.
The larger your fish the more resistant to ammonia poisoning it will be.
As an example, your breeding pair may behave normally as your wrigglers
begin to free-swim but the fry will go straight to the top of the tank
trying to breathe and will be dead within two hours or sooner. This can
happen with such a small amount of ammonia in the tank as to be
undetectable by test kit. This can be overcome with the use of detox
chemicals and by changing as much water daily as you can. Be sure to have
the temperature, pH and hardness as near to the same as the tank water as
you can. I have taken wrigglers on the pipe and their parents and
transferred them to another tank without mishap so don't be afraid to
change your water.
The symptoms of ammonia poisoning can vary depending on the amount of
toxin but it generally begins with a head-up attitude and fast
breathing-not necessarily at the top of the tank-followed by a loss of
vertical attitude i.e. laying over on their side, a heavy mucous (slime)
excretion and fraying of the pectoral and dorsal fins. In bad cases, where
the fish has been saved, the fins can disintegrate right back to the body.
If this happens do NOT medicate as the fins will grow back rapidly
assuming you water parameters are correct. Many people have mistaken these
symptoms for the so-called "Discus Plague" although, on two
occasions, I have had ammonia spikes in adult holding tanks that appear to
have been a precursor to the plague or something very similar to it. I say
this because the usual treatment regimen for the plague had no effect on
the problem. I digress... that is another story.
Nitrite poisoning has the effect of converting the fish's blood
haemoglobin to methaemoglobin which does not allow oxygen to be
transported through the blood. Nitrite has the same effect on humans. The
symptoms are also a perfect match for those of gill flukes and in numerous
cases have been diagnosed as such with devastating results. Fast
breathing, clustering together at the tank top, shimmying and pancaking.
Nitrite poisoning can be slow acting to the extent that it may take two
months for the fish to die from exposure to it. Sea salt or table salt can
be added to the tank at the rate of two tablespoons per 40 litres to give
temporary relief. The chlorine content of the salt prohibits the nitrite
from being absorbed by the gills.
Just a word about how these toxins can be introduced into a tank other
than by water changes.
Biological filtration has an optimal pH range for maximum efficiency.
Unfortunately this is above 7.4pH. As most of us who keep discus run our
tanks under 7.0pH, we need to be careful not to damage the filter.
Probably the most dangerous tank condition as far as biological filtration
is concerned is a "pH crash". Now this doesn't usually happen
fast but takes between 12 and 24 hours. The most common cause of this
crash is the nitrifying bacteria itself. They consume carbonates (kH) to
perform their duties and if the carbonate hardness of your tank is low-as
it should be for breeding purposes in particular-then the buffering
capacity or ability to resist change in pH of your tank is gone and your
pH falls to dangerous levels. The best way to fix this quickly is to add
bi-carb to your tank and raise the pH back quickly. Yes...quickly. You
won't hurt your fish by raising the pH from 3.5 to 6.5 in 5 minutes. Don't
try reducing your pH quickly though as this is deadly to your fish. I do
it quite often because the kH in my breeding tanks is less than one.
Trouble starts when you don't attend to this quickly and your filter
bacteria start to die off with the resultant buildup of ammonia, nitrite
If you learn to keep your water conditions as they should be, test both
your tank and "raw" water at each change-hopefully this is at
least every second day, have some form of detox on hand and study the
behaviour of your fish you will not suffer the tragic consequences of
these two horrendous toxins. Remember, if you are ever in doubt about your
tank's condition, test everything and do a water change...then do it all
Everything I have written about here has come from hard-won
experience...not out of a book.
I have killed more fish out of ignorance and stupidity than most of you
will ever keep so if I save just one fish with my ramblings here then it
will have been worth it. Feel free to contact me if you need any help.
Take care and good fish keeping.