Tony is correct. This is not the past form. It is the passive form. They are in the present tense.
I clean the pond on Saturdays. (active sentence)
The pond is cleaned by me on Saturdays. (passive sentence)
The participle "cleaned" looks like a past tense verb, but it's not. It's actually a type of adjective called (rather unhelpfully) a past participle. The verb is is.
Thank You GM. I really appreciate your clear and well structured explanation. Once again, Thanks.