There are many factors to raising bigger fish in your pond. Ph is important but not the chief thing to address. As mentioned earlier fish are predators and eat smaller fish. If you can see 10 ft down, you are lacking some nutrients that encourage plankton growth. Smaller fish eat plankton, reproduce, get eaten by bigger fish who may in turn get eaten by bigger fish. It's suggested that correct visibility is about 18"-2'. Controlled by the plankton in the water (not mud).
I fertilize my pond from time to time. Our 2 acre pond has Bass, crappie, bream (mixture of kinds) and at least one channel cat. Your pond should have an ecological balance of smaller baitfish to feed the larger fish. Too many of one or the other throws the balance out. Bream are a bass's main diet, same for a channel cat and crappie.
A pond will support X #'s of fish (just like an ag field will only produce X#'s of food). It doesn't care if there are 10 10# fish in it or 100 1# fish. To make a pond healthy requires proper fertilization, and harvesting.
If you supplemental feed the fish you can harvest more #'s per acre. If not it is essential to get the fertilization ratio correct to promote alge and having the correct amount of feeder fish for the bass (fat head minnows/bream etc).
You can buy floating catfish food at TSC (among other places). It will feed the bream/catfish/crappie. At least that seems to be what is eating it when I toss it out.
My 2 acre pond can safely harvest about 50#'s of fish a year. I mainly do that with the crappie in there. I inherited the pond with crappie in it. It's not a good idea to stock such a small pond with crappie/catfish if you want large bass as they compete with one another for the same food sources.
And don't get me started on fish STEALING birds... I have to address them as well.