I have a 73 gallon tank with approximately 20 freshwater fish
in it consisting of 3 Clown loaches
, 2 Royal Spotted Hill Trout, 2 Sumatran Two Spot Catfish, 3 Blue Acaras, 2 baby Plecos, 3 Purple Loaches, and 5 black angelfish. Running a Fluval 405 and an Eheim G3, the Eheim I just added mid-December to my existing Fluval set up - so that bacteria colony is new. Running Matrix, Purigen, and Bio Foam, and BioMax in the Fluval (Biomax and Bio Foam just added yesterday, I took out carbon) and running Eheim substrat pro and mechanical ceramic filter media in the Eheim. I also recently added plants to the aquarium (August) and am dosing them with flourish excel, flourish, and equilibrium - UV light 8-10 hours per day. When doing water changes, I treat with Prime only and the plant products.
Otherwise the tank has been set up for 5 years with no health problems, but recently (in May) I transported the tank across country and did a 20 hour drive. During that time some of the beneficial bacteria in my Fluval died, and due to poor water maintenance, and my filter breaking down while I was out of town and traveling, the fish have suffered from high nitrate elves (50-70ppm) from approximately August - November. The water PH and hardness is also very different from where we moved from, so the fish have been stressed in adjusting to that in addition to the water cleaning neglect. During that time, I lost several fish (not listed above).
The tank's nitrate and ammonia levels are now under control, and have been since early December. Current levels are PH 6.9, Nitrite 0, Ammonia 0, Nitrate 5-10 PPM
Ok so Jan 3rd I returned from vacation and I saw that my Royal Spotted Trout fish had developed an abscess that you see in the picture. Only then, it was pinkish / white fluid filled bubble. The fish was otherwise highly energetic and his usually aggressive self. When I returned from vacation, during a water change
the fish jumped out of the tank onto my carpet floor. I immediately grabbed the net and scooped him up and dropped him back into the tank, and that's when I realized that his abscess has popped, as my white net had bloody puss on it and the fishes flesh was an open flesh wound in the tank.
Since then, I have been doing about 30% water changes every 3-6 days. Due to the high PH from my tap (7.4 I do alter the PH over a period of 3 days to bring it down to 6.9 / 7.0) Temperature is at 80 degrees. The fishes energy levels and appetite remain the same, but the wound size is growing, and he has developed red sore on the top of his back where his dorsal fin starts (you can see in picture taken Jan 4th, since then has grown some) and is developing a similar looking pink abscess on his other side, much smaller, but very similar looking to the one on the picture). His energy level / appetite remains the same.
I am extremely concerned both about this particular fish, as well as bacterial contamination throughout the tank. I am hesitant to treat the tank with an antibiotic due to my pants and the new colony of bacteria in the filter. This does not quite look like septecemia, but it also doesn't look like an ulcer due to the bulgy flesh. I was thinking about making doing a salt dip or even an an antibiotic for the fish? But am also sensitive to his delicate wound. I've never seen anything like this before, and hoping someone here can help. Thanks in advance