Inherited a stagnant pond in rental - water quality and mosquito advice
The Situation:
I’ve recently moved into a rental in Melbourne, Australia with a pre-formed plastic pond that was stagnant and overgrown with a heavy root/grass bed and hundreds of mosquito larvae. It is situated within a rain garden setup with a plastic membrane. The water is very dark ( tannins possibly?) and has had a metallic/mineral smell that has since got a little better since troubleshooting it.
I've no idea how long it's been in this state, we took over the rental about 2 months ago and it has been stagnant and filled with dead and alive "common reed" I think?
What I’ve done so far:
Manually removed the entire root/grass bed. Keeping some of the reed plants to re-establish later.
Drained roughly 40% of the water and refilled the rest.
Added a small amount of dish soap to break surface tension (which hasn't fully cleared the mosquito larvae).
Got the pump/waterfall running.
Currently doing a "flush" by overflowing with fresh water, but the water remains dark/tea-colored and larvae are still present.
The Issues:
Mosquito Larvae: They are congregating in areas where the waterfall current doesn't reach.
Water Clarity: The water is dark like a black tea and hasn't cleared. the pump has been running for a few hours
The Smell: A persistent metallic scent.
Questions:
What is the best way to maintain this pond going in to the Future?
Should I do a 100% drain and scrub to remove the silt at the bottom, or will the pump and native plants eventually clean the pond?
I read that removing all the water can rid the natural bacterial and ecosystem?
What’s the best way to deal with the larvae in a "dead zone" without using heavy chemicals?
Is the metallic smell likely just mineral oxidation from the lava rocks/scoria or is there something wrong with the pond?
Ideally I'd love any solutions to be native focused and environmentally conscious