Gunk in the water bowl?

I switched Tibbs and Peter from a bottle to a water bowl a few weeks ago (on Hopper advice - ta muchly) and they love it. I am getting a bit frustrated though - it seems like every other day I'm having to really scrub it out with wire wool because there's green gunk on the bottom and the sides, and my fussy pair wouldn't touch it! I don't mind, but seriously, is there any way I can reduce this stuff? Anyone else have the same problem?

I'm not having that problem yet, is the bowl outside or where sun can reach it?
All I have at the moment is hay and fur

That is really odd. What kind of bowl is it? I have ceramic bowls and have used them forever, they only ever need a quick swill out and theres nothing ever been in them like that before. How strange X

I had that problem when I used a metal bowl for Chewy's outdoor balcony, so I switched to a ceramic bowl and it doesn't get that anymore.

putting it in the shade may also help it, as i know the sunlight speeds up the growth of the green stuff that grows in bottles ... could it be the same thing?

I only have that issue in the summer and find sterilising the bowl once a week with hot water seems to keep on top of it, so if it is happening really quickly I'd second the suggestion of keeping it in the shade.

Thanks guys, it's a terracotta bowl that I pinched from work I'll run it through the dishwasher to sterilise it and then move it into the shade. It just seems to grown much faster than it ever did in the bottles and they were always in the sun.

The bowl is open to the elements and anything that drifts into it, unlike the sealed container of a bottle.

Ah....

sounds obvious when you put it like that

MY water bowls in the garden are going green in a week at minute