Some sand sifters EAT the beneficial organisms in a sand bed and cause further issues, IMO...sand sifter stars, sand sifter gobies.
Some sand sifters eat detritus and are good...many snails, sand sifter cucumbers, brittlestars.
If you are trying to correct an problem with brown slime algae or diatoms, these do nothing other than hide what can be a serious problem brewing. adding more animals does not help, and can cause further issues.
Some of these animals may well starve, such as sand sifter stars, causing further issues as well.
While IMO sand sifting snails are well placed in most systems, others require particular particle sizes (sand sifting cucumbers).
This is a complicated question, and it is important to know what you are trying to accomplish. In a reef tank, I would be unlikely to have a sand sifting goby...and certainly not if you are just trying to resolve some sort of algae problem.
So it is absolutely critical to understand what you are trying to do to assess what you need to do or add.
If just a "healthy" sand bed, then you need sand sifter snails.
But since you are not having luck with the goby (I don't know what this means), then it is likely something more. In this case it is very unlikely that a fish will resolve your problem. Many will simply add to it.
Nuisance algae or detritus problems on sand are a combination of factors that need to be addressed, usually with maintenance and equipment before adding more animals.