gold fish in pond dying

Question
QUESTION: Hi
Don't know where to turn, and found this website.  I am in South Florida and have a pool, converted through the courtesy of Hurricane Jean and Francis 2 years ago, into a pond for goldfish.  Has been doing OK for 2 years now.  Is a normal size built in pool and has about 50-100 goldfish in it.  It has a pump for continual aeration.  The water is green, and 2-3 months back introduced some pond plants - lily like.  They thrived and all seemed happy.  Fish would gather and swarm when fed every morning.  About a week or so ago, placed another group of the same plants in, probably about 10 or so, bringing the total to about 20.  They cover maybe 2-3 max 5% of the pool.  The old ones are fully green and health looking.  The newer ones, obtained from the same pond, seemed brown and a bit burnt when brought it,but the originals may have been too.  The last 2-3 days the fish all seem to be at the surface breathing, especially where the pumped recirculated water goes back in, and not interested too much in the food.  I have also had about 2 a day for the last 3 days dead, floating atop,
I have added an algae cleaner tday that clumps it and makes it float.  Also, about 3 weeks ago, when concerned over the price of the goldfish food bags - about $39, the fish girl there said that cat food could be used, so have ben using that (9 lives) mixed with the remaining pellets.  Am also loking for an ultraviolet light to put in, as that has also been mentioned to help algae growth, which I am assuming is depleting the oxygen from the pool.  Am I on the right track?
Any help wil be greatly appreciated by myself and the fish.
Thanks! Kind regards, Bob

ANSWER: Bob, there are many reasons the fish could be dying. I will do my best to point out everything that I can think of. Fish gasp up at the surface when they need more oxygen. There is usually an underlying cause for such behavior.

1)Something leached into the pond that is harmful to fish; i.e. lawn fertilizer, insecticide, oil from a pump, etc.
2) Did anyone treat the lilies you put in recently with anything?
3) Hold off on the algaecide until the other problems are solved. Algaecide takes air out of the water. If the fish are oxygen starved using algecide is only contributing to the underlying problem.
4) Test your water for Nitrite and Ammonia. You could have a waste build up occuring. Fish will die off 2 or 3 at a time until the problem is handled.

You are on the right track with a UV. The keep the green out if used with a filter. Please let me know how this turns out or are if we have not helped solve the problem.

Thanks,
Brigitte
www.pondmarket.com

---------- FOLLOW-UP ----------

QUESTION: Hi Brigette
Thank you for the useful info on this. I stopped feeding them, and fortunately have had no floaters in the last 2-3 days.  Do you think it may have been the dry cat food?  The first 5-6 days of it were ok, then they started dying.  I had previously used another brand of cat food about 2 weeks before, and a few ended up dying later that day.  Is there another cost effective substitute other than the pellets for the fish??
Also, I don't have a pool filter, but am I to understand the UV light is something that is incorporated into the filter system?? Or is there another type that can be put in by itslef?
Thanks again Brigitte.
Best
Bob

Answer
Hello again, Bob! If there are fish in the pond it will need some sort of pond filter sooner or later or the water will get poisenous from the fish waste. The food you have been feeding probably contributed to that problem. Good pond fish food is formulated to produce the least amount of waste (fish poopoo).
There are UV lights that work independently of the filter, but with fish in the pond you should either a) have only a few Goldfish and NEVER feed them (they will nibble on the plants and algae to get enough food) or b) have a pond filter.
Brigitte
www.pondmarket.com