Question
Hiya
I've had a pond now for about 3 years so is well established but about 2 months ago restocked my pond with baby fantails(1.5") & koi (2-3 inch) 6 of each. Within the last 2 weeks I've noticed:
Spot (koi) has a missing bottom tail fin
Ugly has an ulser by it's top fin and a cloudy eye
Amber has green like dots on it's body
Blacky my blackmoor has raised body scales and has puffed up bodily.
Fancy - one of the fantails is laying on it's side and is unable to swim upright.
One of the fantails died without any signs of anything wrong.
They all eat well - I feed them 10 floating koi pellets per day and occasionally (1 every 2 wks) a torn up lettuce leaf.

So where am I going wrong and how can I treat them?
Thanks  

Answer
Did you have other fish in your pond when you added the new fish?  Did you quarantine the new fish?  How many new fish are there?  How big is the pond?  It's good to quarantine because the new fish may have brought something into the pond.  Missing fins are usually due to physical injury such as spawning or other fish nipping at the fish. Sometimes, missing fins can be the result of fin and tail rot.  Ulcers or tumors have many causes from bacterial to viruses.  Cloudy eyes can be due to bacterial infections, injury, or rarely eye parasites.  Green dots on a fish are usually algae growing on injured areas that are often infected.  Raised body scales and puffing out is dropsy whihc is an internal bacterial infection.  Trouble swimming and laying around (lethargy) can be related to almost any health issue (parasites, bacteria, funguses, swim bladder problems).  

When you buy new fish, it's not uncommon to lose a few percent of them but if you lose more than 10%, there is probably something really wrong.  It sounds like your fish have a variety of ailments.

First, I would test your water to rule that out.  Test for pH, hardness, alkalinity, ammonia, nitrite, and nitrate if you can.  Then, I suggest doing a partial water change.  Aerate and filter the water well.  Add dechlorinator equal to the volume of new water.  Add pond salt at 0.1% if you have no plants and 0.05% if you do have plants.  As far as stronger medications, it sounds like various fish might have bacterial issues, injuries, and more.  MelaFix is an all natural, safe antibiotic that may help some.  The fish may need a stronger antibiotic; I prefer erythromycin since it doesn't kill the good bacteria like some antibiotics.  Unfortunately, the dropsy that the black moor has almost never gets better but that doesn't mean you shouldn't try the salt and antibiotics.

Also, see http://www.fishpondinfo.com/fishcare/treat.htm

I'm sorry for the delay in response; my family was out all day yesterday, my one day of vacation this year at the theme park.

Good luck!
Robyn