Footage sent to the Express & Star by Kulvir Bains shows hundreds of dead fish being cleared away from West Park in Wolverhampton on Tuesday morning.
Dead fish have also been seen in pools in Lichfield and Perton.
Wolverhampton Council has said that the cause of death of the fish is the warm weather and thunderstorms that hit the Midlands this week.
Mr Bains, from Wolverhampton, said: "It's horrible to see these dead fish. All of the older people who come down here to watch the fish and the pond saw all of this, it's horrible.
"It's a filthy pond, so it might be down to that. There is always some sort of rubbish in there and algae, it's filthy. It needs cleaning."
Wolverhampton Council has said that the mass death of the fish is due to the recent hot weather and thunderstorms experienced in the Midlands, also saying that they are working with the Environment Agency to "manage the situation".
Kieran Newman, 43, of Wolverhampton, said: "It's disgusting to see this many dead fish. I have been coming here for well over three years and love feeding the fish where I can.
"It's a shame, I think it's due to the thunderstorms and the heat, I know sudden heat changes can kill fish. I just hope something can be done."
Footage was also sent to the Express & Star by a resident in Lichfield who witnessed hundreds of the dead fish float downstream in the Rive Tame in Elford.
Simon Turner, from Elford, said: "We have just observed literally hundreds of the dead fish floating down the River Tame in Elford down stream of Tamworth. Clearly river pollution."
Craig Widow, an angler from Staffordshire, added: "I have seen a few dead fish around yea, it's definitely more than normal which is quite concerning.
"You usually get stuff like this happening after thunderstorms I think, it's not out of the ordinary, it's still sad to see though."
Councillor Craig Collingswood, cabinet member for city environment and climate change, said: "We are aware of the death of fish in the lake at West Park and are working with the Environment Agency to manage the situation.
Councillor Collingswood said that the situation is a natural result of warm weather conditions, which trigger algae blooms, which can reduce oxygen levels in lakes, leading to fish being distressed and in some cases, dying.
The councillor went on to say that weather monitoring is ongoing, and measures are in place to safeguard future wildlife.
Councillor Collingswood added: "We have been monitoring the weather forecast and installed an aerator in the lake more than a week ago.
"We have now installed a second aerator to help boost the oxygen supply. We will continue to work with the Environment Agency to ensure oxygen is at the required level."
The council said the fish are being removed and will review whether to replace the dead fish over the late autumn and winter months.
The council also advised people to "stay out of the water at all times".
A spokesperson for Pipehill fisheries, on Walsall Road, Lichfield, said: "A few of pools of the pools oxygen levels dropped, I think it was two our of three of the pools dropped, but we turned on the extra pumps and we managed to get through it without any incidents.
"There is a lot of factors that go into the safety of the fish to be honest, we have also had a bit of cross wind on the night time too, which will stress the fish as well, but we are on top of it."