keeping the water in the rainwater barrel clean

[Dilbertian]

Do those silvery oval discs work to keep the water clean?

The water in one of my rainwater barrels is always perfect. But the other one has never been right. Just before the heatwave the water smelled utterly foul, like rotten eggs, and the inside of the tank was covered in brown scum. I blitzed it with thin bleach (like concentrated Miltons) and drained the tank after a week. The scum was all gone and the water smelled like a swimming pool.

I want to prevent this from happening again. Do the silvery discs work?

No idea but following as my brand new water butt smells foul.

Mine are huge whisky barrels, the tap st the bottom was clogged with the scum/slime so we were filling from the top. I popped a few oxygenating plants that youd put in ponds in and its been fine ever since

Lovely solution, but ours are closed on top for safety, so plants wouldn’t work.

But its going slimy due to lack of oxygen??? Thats where the slime comes from.

Anyways, you do you. Its basic biology.

Could you have a grill/grate at the top for safety bit would still let the light through?

grate on top then goldfish works really well

I have two, both with locked tops. One is always perfect, but the other, the one that went sulphurous, has never been quite right.

i wonder where it’s anything to do with the roofs that they drain? The good one drains from a tiled roof, the other drains from a ‘felt’ roof. Not felt, exactly. Some sort of waterproof roofing stuff that comes in a roll.

Worth considering.

The barrel is tall and narrow. I can’t see the bottom if it’s full when I take the lid off and look in. Would the plant have to be at the bottom? If I hang some pots in the water so that the plants get light, would it keep ask the water clean?

I have taken the top off mine for a bit to see if it helps, musing on adding some Ecover 🤣

I bought something to treat the water with, but then discovered that you have to empty all the water, scrub it out & fill it back up again with the solution added, mines fixed to the wall so would be difficult to scrub out.
What sort of plants? Can the just float on top?