Algae is a multilayer topic. But in general it´s always the same: The more nutrition there is in the water, the more algae you get. So it is necessary to keep the pond as clean as possible. For this, ideally install a powerful filter. All this is more important than algae remedies - but you can use them additionally. The mentioned fish usually have enough nutrition and need little feed. Eventually you should shorten the feed so that there is less nutrition in the water.