Fantail with red streaked tail and fins

[herbie53]

I've had a fantail for around five years now, he had shared a tank with another goldfish for 4 and a half years until this goldfish unfortunately died. About 3 months ago I added a new goldfish to the tank. The fantail is approximately 10.5 cm in length (excluding the tail) and lives in a 50L tank. I perform a 20% water change each week and use a water treatment to remove ammonia and chlorine compounds. Since the fantail's problems have developed I have purchased a new Fluval filter with a disposable cartridge. I tend to rinse the cartridge out in treated water every 2-3 weeks. The tanks has a gravelled bottom of depth approximately 3 cm and I use a gravel vacuum to clean it. I currently have two plants in the tank and have had these for the past 3 months. I feed the fantail some Koi pellets and the other goldfish some smaller pellets. I remove any food which hasn't been eaten after around 2 minutes.
Temperature - 20 degrees
PH - 7.5
Ammonia - somewhere between 0 - 0.25, hard to distinguish colours in test kit
Nitrite - 0
These results are before water change
For the past 6 weeks the fantail has been displaying red vein-like streaks on its tail and fins. Over the last two weeks the red streaks have become more pronounced and seem to now cover a large amount of the tail. The fish is still eating and swimming but appears to have slightly lower energy levels than normal. Whilst there are read streaks there are no red blotches on the body. The other fish in the tank is displaying none of these symptoms
Initially I assumed it was to do with water quality so I conducted some water changes and bought a new filter. However this didn't improve his condition after about a week so I went to a pet shop and they suggested it could possibly be fin rot. I used some fin rot medication but this has had no impact either.
I'm completely puzzled by what the cause of his condition could be any would be very grateful for any suggestions!
Thanks alot

 

[jsoong]

Red streaks in the tail is usually some kind of infection. The most likely reason for this is water quality issues.

50l is a small tank for goldfish. It is just barely able to cope with 2 fantails. <A 20 or 30 gal = 80-100l is much easier to manage.> The key to managing goldfish in small setups is water change. <Of course a bigger tank will be much better!> A better filter will help, but there is no getting away from pwc's to remove toxin buildup.

Even though you have no measurable NH3 or NO2, other stuff (like dissolved organics) and nitrates do accumulate & weaken the fish to produce illness. If you have not done so, check the nitrate levels. Small goldfish tanks often have nitrates up in toxic levels (like 100 or 200). Also check the pH compared to tap ... again, a lowered pH is another indicator of toxin accumulation.

Even if all tested out fine, I would increase the water change amount. For a small tank like yours, i would do 50% pwc weekly at a minimum, if not twice a week. <Fanatics will do daily pwc's in small setups.> Clean water is your first defense against disease.

Although it is tempting to just treat the symptoms, it is typically useless unless there is pristine water conditions. As for what the infection may be, the most likely is an internal bacterial infection. <Usually an opportunistic bacteria that attacks weakened fish ... 5-6 year old is old in terms of fancy goldfish (typical life span is 7-10 years) so immunity is likely less than the new fish.> After fixing the water, I would be tempted to treat either with an oral antibiotic (ie antibiotic in food). External treatment tend not to work well for this as the drug won't get into the fish (goldfish being thick bodied). The only role for external treatment is if you suspect some external parasite that created a wound to allow for bacteria entry. <For this I usu. just use salt, but salt will kill your plants at doses needed - 0.1% to 0.3%. Of course, you can remove the plants to a holding tank during treatment.>

If you do decide on antibiotics, try to find food that contain kanamycin. That is the current best treatment for goldfish.