Racing Victoria stewards will contact the managing owners of 81 starters involved in the Aquanita 'top up' case to ask them why their horses should not be disqualified.

Senior Aquanita staff including trainers Robert Smerdon, Stuart Webb and Tony Vasil were issued varying disqualifications by the Racing Appeals and Disciplinary Board in 2018 for dishonourable or improper practices which chairman Judge John Bowman described as one of the darkest moments in Australian racing history.

Last year the Victorian Civil and Administrative Tribunal dismissed Smerdon's appeal but altered Webb's and Vasil's penalties.

Stewards have determined that 81 starters of 395 potential treatment instances should be considered for disqualification based on actual administration findings by VCAT.

On Tuesday stewards wrote to the managing owner of those 81 starters with a show cause notice advising them of their preliminary decision, giving them until August 10 to respond as to why their horse should not be disqualified.

Jamie Stier, RV's executive general manager, integrity services, said it was a unique and complex case.

"Text messages between the disqualified persons were central to the RAD Board and VCAT's findings regarding the participants' improper or dishonourable action, or practice," Stier said.

"However these texts often referred to multiple horses or lacked clarity around which horse was the subject of said practice on a given day.

"Accordingly, while the evidence made it clear that those charged had engaged in unlawful practices, determining which horses were subjected to those practices was not possible in all instances."

Stier said of the 81 starters considered for disqualification, 24 were winners, 24 minor placegetters and 33 were unplaced.

Prize money won by each varied from $300,000, to none at all, with more than half winning less than $10,000 in the race in question.

A timeline has not been set for when stewards will make a determination as to when those starters may be disqualified and a decision has yet to be made if any prize money will be required to be paid back, should any starter be disqualified.