First things first, who do you mean by “strata”? The strata manager, the strata committee or the building manager?
Either way, if you are an owner you can petition the committee (with the support of other swimmers) to alter the opening hours.
If you are a tenant, you can ask the landlord to do the same, or reduce your rent due to the loss of amenity.
If this has happened because some residents have complained about noise from the pool, there must be better ways of dealing with this than shutting the facility completely.
As a last resort, you could threaten to take the strata scheme to court or a tribunal for unreasonable removal of an essential facility which was part of the reason you bought into or rented in the scheme in the first place.