I have black-colored mold that grows in one of my bathrooms on the toilet bowl under the water's surface and on the tub/shower curtain. I clean it, but it always comes back in 1-3 weeks. It does not appear elsewhere.
Any ideas? Is there a cheap test I can do on the water?
How do you clean it? I'm no expert, but I'd turn off the water to the toilet then flush it till it's empty, then hit it with some mould spray. I'd look at the water tank too (which should now be empty) and give that a clean too. Read the instructions on the sprays cos you're meant to leave them for 5-10mins to do their work before you wash them off. Then turn your tap back on and see how you go.
Remove it with vinegar, it will stay away longer, although it won't remove the root cause.
The root cause is that you have a source of moisture there, allowing these fungi to live. Maybe your toilet has a pin leak, or that spot is a bit colder than the rest of your bathroom, leading to moisture condensing there first. If you remove the source of moisture, the mold will be gone too.
Any ideas? Is there a cheap test I can do on the water?
I don't know if it's a danger or not.