Dr.,
You will get much better and broader recommendations from others on this forum but I will chime in on a few things...
18" is not "very clear." I would say that is perfect assuming the reason is algae in your water and not something else such as particulates.
You already have 12+" bass in there so stocking 4" or smaller copper nose bluegill (CNBG) will only result in food for the existing bass. I've read here that LMB will eat bluegill(BG) up to 1/3 their length.
As for the "big" bass(LMB), the only reason you would want to add large bass is if you have an over-population of BG (and/or other smaller prey) or to ensure they do not get eaten by already existing larger bass.
As for channel cats (CC), I stocked them in my pond along with BG and LMB and have been sorry. They are difficult to catch and will prey upon BG when they get bigger (I did not know this when it was suggested to stock them). Some people really like CC but I don't have a particular affinity for them; just thought they would "add" something to the pond.
There are alot of other questions that need to be answered. A fish "survey" likely needs to be done on your pond to get the overall sizes and populations of all the fish types swimming in your pond before a comprehensive plan can be put into affect. With that said, I would be cautious of a supplier "pushing" big (and way more costly) fish.
Dan
1 ac pond LMB, BG, RES, CC
