Fish Going Black

Question
Hi Robyn. Please can you help? I have a small, round raised terrace pond (approx. 50 gals) with six small fish: two goldfish and four Golden Orf. The pond has many water plants and is filtered using a Hozelock Cyprio EasyClear mechanical and biological pump with UV light. The pond is about 12 months old. All of the fish appear to be very active, although I have just noticed  that one of the Golden Orf's tails is going black in colour. I'm sure this is not normal and am concerned it may have a desease, the fish feeds well and is a lively as the other (as yet unaffected) fish. If you have any suggestions what this may be and how it may be treated I would be most grateful. Thankyou.  

Answer
First, let me say that I am so sorry that I was unable to reply to any e-mails yesterday.  We have slow dial-up at home.  It rained and rained.  The underground phone lines were waterlogged.  I was unable to maintain an internet connection long enough to do anything.  So, I had to wait until I got to work where we have fast internet.  The problem is, they expected me to do "real" work and not help you so I was unable to get to your message until now.  

Golden orfe have black mottling on their backs and some may extend into the tail.  Without seeing a photo, I can't say for sure if it's normal.  Hopefully, it's nothing to worry about.  I can tell you that a 50 gallon pond is not large enough for more than a few goldfish and not large enough for any orfe long term.  My orfe are 1.5 feet long.  Orfe should have at least 1000 gallons.  How big are your fish?  As they grow, the ammonia will probably spike, and the fish may start to show signs of distress.  I doubt that would cause the tail to turn black.  I would check your ammonia and nitrite levels anyway.  I hope you can build a bigger pond.  Orfe are great fish!  My page on them is at http://www.fishpondinfo.com/orfe.htm
Good luck!

Robyn