Have you looked into adding any aeration? Aeration can pay big dividends in controlling algae, especially in an earthen bottom pond. There are also other things like dyes to help filter sunlight where your other aquatic plants are not. Our company helps a lot of people with large ponds control algae and w/out hazardous chemicals and one product talk to people about is GreenClean Pro as it is safe for all types of aquatic life. Combine that and some beneficial bacteria and you have a solid 1-2 punch for controlling the algae. As someone mentioned earlier, oxygen depletion can result if you kill too much algae too fast, however you also must realize if you kill algae and it is left to naturally decompose, it will simnly fuel another round of algae unless it is removed or broken down by bacteria. Here is a link that might be useful: Pond Algae Control

while small yes, when they get bigger they tend to get aggressive with other fish. I go with bristlenose pleco's. They stay relatively small and don't bother the other fish.

That is the best thing to do for green water! A UV light will clear it by killing the green algae, then the filter can clean it out of the water. Then the plants can help keep it clear. A UV light is a well spent investment.

Not so long as you maintain consistently adequate levels of the most effective algaecide: Chlorine. One exception to that is if you close your pool in the winter. In the case shocking your pool, following a couple of days later with a double dose of PolyQuat 60, and following that by bringing the water to a high normal chlorine level right before closing can keep you from opening to a swamp.