in an aquarium shop, you might be able to ask
the owner if any of his remaining discus have
begun to exhibit the small black spots.
The fact that your two blue discus are
not showing any spots indicates to me that
the tomatoes are not carrying any disease.
Nothing was said regarding the water readings
in the tank. How about the temperature and
the pH? If the fish are but a few months of age,
it’s possible that they can be going through a
normal color change—with the black spots
being part of the normal pattern change in
your tomato discus.
If you were fortunate enough to see the
parent fish, you might have seen spotted
tomatoes. Your fish may be highly inbred
specimens, in which case black spots or
other pigmentation abnormalities can appear.
And it’s possible that as your fish mature
(assuming they are not mature), you may
find that their color pigmentation will even
change a bit more. The pigeon blood discus
developed by Kitti Panaithi in Bangkok,
Thailand have gone through many color
changes, with the initial black coloring now
being totally absent. Stay with your tomato
fish—they sound interesting to me.
I would like to begin by pointing out that,
in my opinion, TFH magazine is unrivaled
in its presentation and content. Now, I’ve
been at this hobby for some time, but this
issue has me stumped. I keep discus and
currently have eight in a 45-gallon high
display tank in my office. Five of them are
gorgeous fish from Asian breeders, and,
yes, I have three of your beautiful fish.
Strictly speaking, there is no problem yet,
but something is taking place regarding my
water chemistry, and I simply cannot figure
out what it is. Okay, I call that a problem.
I once used strictly RO water during water
changes; I like to know what’s going into
the tank. I would utilize a reconstituting
product and a pH buffer to fix the pH at
about 7. Over the past several months, I
have been adding only one half RO water,
and the rest tap.
I stopped using the reconstituting
product because I believe that the trace
elements and water hardness will now be
contributed by the tap water (I am still
adding the buffer, however). The tap is
hard; water testing has shown a pH above
8. Since I began this new regimen in the
beginning of October of last year, my pH
has slowly, but steadily, dropped from 7. 2
Discus tend to do best at a pH of 7. 2 or lower.
I’ve been told that the tap water has
been sitting in those copper pipes for some
time, and that I should aerate it. I’m told I
will find that it’s lower in pH than I think.
But how much lower? Does it matter?
Whatever the pH of that tap water, it will
certainly not be lower than the pH of the
stripped RO water.
I naively thought that, whatever the
property of that tap water, I would be
noticing a slight rise in pH, or perhaps not.
But how in the world does adding tap water
to RO water that has been successfully set
to a neutral pH result in a decrease in pH?
My tank is 45 gallons and has eight discus,
assorted cory cats, and cardinals. Here are
my water parameters: ammonia 0, nitrite 0,
nitrate 8 to 10 ppm, temperature 82°F. Any
help would be greatly appreciated.
New Bedford, Massachusetts
Your letter shows me I don’t have many
guidelines to help. I see that you probably
don’t have a reliable pH meter, nor a hardness
test kit. You are told you will find your tank
pH to be lower than you think it is—with
your questions being how much lower and if
I’ve never used an RO reconstituting
product, so I must move on from that. You
were told your municipal (tap) water has
been sitting in copper pipes for some time,
and that you should aerate it. By all means,
yes, flush all standing water in the pipes at all
times—for regular kitchen work, aquariums,
drinking water, etc. Your local aquarium
shop will have what you’ll need for water
If you are using tap water and RO water,
we must know what percent of each is used,
as well as the frequency of the water changes.
Most Massachusetts municipal water is not
hard and is soft enough to be very acceptable
discus water. You tell me your aquarium water
has slowly dropped from a pH reading of 7. 2
to 6.0. Although a pH of 7. 2 is acceptable in
most discus tanks, your pH reading of 6.0 is
better. Has it dropped lower than 6.0?
Remember that your RO water has virtually
no buffering capacity, so you can regulate
your water pH by adjusting and maintaining
the proper percentages of both your tap water
and your RO water. And obtain a quality pH
kit or pH meter. You do need one. D
Tropical Fish Hobbyist