Question
good morning Robyn,

we mov ed into our house 2 years ago and inherited a nice ornamental pond, i've no idea how many gallons of water it holds but its 8ft in diameter, the shallow point around the edge is about a foot deep and the middle is about 3 ft deep. i saved my inlaws goldfish last year, approx 40 of varying sizes and all seemed fine until this week, we have several fish lying on their side on the top of the water, 1 has died so far. there was also a good sized frog lying on his back in the bottom, i fished him out and he brightened up a bit. i took a couple of the fish out and rubbed their under belly(i heard this can stimulate the air sacks?) and they also brighted up. i've gcleaned the filter and pump and turned on the fountain to try and oxygenate the water. do you have any ideas for me what else i could be doing or looking for?
thank you for your advise in advance.
kind regards
jonny

Answer
So, none of the fish or frogs has actually died?  For them to be unresponsive until touched means they are in bad shape.  Where do you live?  What is the temperature?  What kind of filtration and aeration do you have currently running?  If it's cold, has there been ice on the pond?  Is there an opening in the ice?  If it's warm, there are different questions.  If the water movement or aeration was off, and it was overly cold or overly hot, then the oxygen levels may have been two low.

Whenever there is a problem, you should rule out water quality by testing the pH, hardness, ammonia, and nitrite levels.  Then, a partial water change with added dechlorinator and pond salt (<0.05% in most cases) is a good idea.  

Rubbing a weak animal often will get a response.  I don't think it has anything to do with their swim bladders (I guess what you mean by air sacks).  It sounds like the problem was not that they couldn't swim right because they weren't moving at all, right?

A pond that's 8 feet in diameter and a foot deep (perfect cylinder) is 377 gallons.  One that's 3 feet deep is 1131 gallons.  If you have half the bottom at a foot deep and half at 3 feet deep, then it would be 754 gallons.  That's a nice sized pond.

I hope we can figure out what the problem is.  I need more information to make a better guess.  It's usually a guess because a pond involves so many factors.

Good luck!