Your pond doesn't produce big fish. Or lots of fish. Or both. There's potentially several reasons why. Let's address the most common.
If your soil has low pH, then probably your pond has low water hardness. You can use a pool kit to test, or bring a water sample to a pool supply dealer and let them test. If the hardess is less than 20 ppt calcium carbonate, then you have an issue.
Many years ago I took a pond management course and one of the first things I learned was that biggest impediment to fish production was low water hardness. Most community water coops define anything above 150 ppt as "hard". There are very few lakes in the country that measure over 100 ppt. One of those was False River near New Roads. At one time, it had one of the highest gamefish populations of any lake in America. The fly fishing on that lake was incredible. Due to environmental reasons, False River now gives false hope to anglers.
To get the hardness of a pond up, just add lime. Simple, right? Until you calculate the amount of lime required. For a 7-acre lake - like the one we had in our neighborhood - getting the hardness up from 20 ppt to 50 ppt required 8 tons of ag lime. Fortunately, ag lime in bulk is fairly inexpensive. And if you have a little help from friends, delivering it into your lake can be done in a half-day.
However, timing and delivery method are extremely important. CaCO3 has very low solubility. It's also unusual in that its solubility decreases as the water temperature warms. Another property is that carbon dioxide dissolves it readily. So... to get the maximum effect, the pond owner should apply lime in winter both directly to the pond in shallow water, or along it's banks. The spring rains - which contain moderate amounts of carbon dioxide - will help increase hardness even further.
With the 7-acre lake I mentioned, we undertook the project in early February. By late April, the water hardness was up to 40 ppt. At that time we went ahead with a fertilization. Let me make this clear: fertilizing a low hardness water does nothing for it. Period! Previous attempts at fertilizing this pond had no impact whatsoever.
After the liming - and the doubling of the hardness - the fertilizer worked miracles. The pond color turned from dark yellow to a rich green. Within a year, the hardness had increased another 8 ppt and the bluegill and redears were big and thick. The shad population exploded. The bass took every advantage of all this protein and soon we had loads of multi-pound fish.
Now the liming and fertilization certainly made a big difference. But during this time we also undertook another project where we added vegetation and structure. The combination of all these things turned our neighborhood lake into a small fishing paradise!
