Algae or mold?

[SinLA]

How do I tell the difference and do I need to be concerned if it’s algae?

 

[wellington]

Black mold is dangerous. Usually grows where there is constant moisture like bathroom showers/tubs etc and it's usually where you cant see it very well, not a lot of light exposure.
So my guess would be more of an algae. The clay saucer should easily scrub off or set it out in the sun and it should disappear. The door will need to be scrub, probably a bleach solution, and then I would repaint it or wash it monthly or weekly depending on how often it starts to appear with the diluted bleach.

 

[SinLA]

Black mold is dangerous. Usually grows where there is constant moisture like bathroom showers/tubs etc and it's usually where you cant see it very well, not a lot of light exposure.
So my guess would be more of an algae. The clay saucer should easily scrub off or set it out in the sun and it should disappear. The door will need to be scrub, probably a bleach solution, and then I would repaint it or wash it monthly or weekly depending on how often it starts to appear with the diluted bleach.

Hmm, both are water bowls. The one on the right is plastic:

https://www.amazon.com/Venetian-Flower-Box-Saucer-Rectangular/dp/B07X43W1DS?tag=exoticpetnetw-20

 

[wellington]

Hmm, both are water bowls. The one on the right is plastic:

https://www.amazon.com/Venetian-Flower-Box-Saucer-Rectangular/dp/B07X43W1DS?tag=exoticpetnetw-20

OMG the one looks like a door on my phone lol.
Well then scrub them both or dump the water and leave out in the sun.
My tortoise and outside dog bowl gets like that. Longer it sits, the darker it gets.