Cleaning Stained toilet when have a septic tank

[CatchThatCat]

I used to soak the bowl with thick bleach for 30 mins which dealt with this but our septic tank doesn’t like too much bleach. Are there any effective alternatives as there’s an annoying dent bit that a brush doesn’t really reach.
I wonder if there’s a way of emptying the water Slightly too to clean better?

You can empty it to clean
www.bobvila.com/articles/how-to-drain-a-toilet/

Isn’t Coke supposed to be Good at cleaning toilets?

Bicarbonate of soda and vinegar?
gocleanerslondon.co.uk/blog/how-to-clean-toilet-bowl-fast-easy/

That is so satisfying it’s easy to empty - I think it’ll really help to clean it . Thank you so much

Pour a bottle of cola down leave overnight and flush

I might try that as couldn’t find a tap to close to drain the toilet bowl