Left to its own devices a freshwater area will attract, guess what, the worst invasives on the planet first (no surprise there) when theres a fertile empty spot, what else can happen...
Its not a bad idea to introduce plants that have favourable characteristics before that happens, give them a head start before nature rules despotically. Natures rule is for one species to arrive at a habitiat every ten years, so the local 'thug' plants get quite a head start...
Introducing the likes of cyperus, pickerel, aquatic iris, water lilies, say a dozen species of year can diversify a habitat so there are all sorts of niches developing for beneficial insects to provide a steady supply of protein for the higher end of the food chain...
Plants with positive characteristics which are steady growing create sheltered shallows, shaded cover from predators, food for grazing, these can get to dominate and make functional the 'empty areas' so in the long term you have everything working for your priorities, rather than against them...
Regards, Andy
