Last year, I lost all my Goyder River Tris (11) from a community tank of
rainbows. A couple of the deaths were from ulcers (the two largest), the
balance were young fish (approximately 12- 18 months old). The young fish
stopped eating and showed signs of discolouration prior to death. When I
say discolouration, the fish were a dark colour in the rear half of the
body. I am not sure whether the discolouration is a symptom of TB. The
water in my aquarium was soft (around 90 ppm) and a ph of 6.8 to 7.0. No
nitrite in the water. Water changes were done fortnightly at a rate of 50%.
No other rainbows in the tank, which included boesmanis, Giddy R Tris, Coen
R Tris showed any signs of ulcers or similar discolouration.
Since I added shell grit to the filter, bringing the ph up to around 7.2 to
7.4, and doing water changes weekly at a rate of 30% per week, I have not
had a recurrence of this problem. Its been about 6 months since I lost all
those Goyders, and the new Goyders I now have seem to prefer the more
alkaline conditions. I too "fast" my fish once a week, and I have reduced
the daily feeding to once per day for the adult fish. The fish appear to be
healthier as a result, and more disease resistant.
Neil Armstrong recently suggested that he believed that tannic acids from
driftwood and leaves is beneficial to the health of rainbows, as the acid
kills bacteria. I don't have any driftwood or other substances leaching
tannic acid in my tanks, but has anyone experienced beneficial effects of
tannic acids with their fish ??
Chen Leong