A stable employee charged with administering more than 100 illegal race day treatments and whose text messages are central to the Aquanita bicarb allegations will not participate in the inquiry.

Racing Victoria stewards downloaded 17,000 text messages from Greg Nelligan's phone, some referring to "top-ups", as part of the investigation into seven years of alleged race day administrations of alkalinising agents.

Nelligan was "moonlighting" for other trainers outside the Aquanita racing banner, the Racing Appeals and Disciplinary Board heard.

Defence counsel Paul O'Sullivan said Nelligan and his wife Denise would not take part in the hearing and wanted to plead no contest to the charges.

But RAD Board chairman Judge John Bowman said no contest only applied in America and it would have to be treated as a not guilty plea.

Group One-winning trainer Robert Smerdon, who like Greg Nelligan was charged over more than 100 alleged race day treatments between 2010 and 2017, reserved his plea.

Trainers Tony Vasil, Stuart Webb and Liam Birchley, disqualified trainer Trent Pennuto and Smerdon stable employee Daniel Garland all pleaded not guilty through their lawyers on Thursday.

Vasil wants the charge against him struck out.

His barrister Patrick Wheelahan said there were many statements by different people about what "top-up" meant.

He said there were only four texts, or four small groups of texts, among the 17,000 on Greg Nelligan's phone that involved Vasil.

Wheelahan said there were examples of other trainers who communicated with Nelligan who were not charged.

"Mr Nelligan is said to be moonlighting," Wheelahan said.

"There are references to other trainers outside of Aquanita that he is communicating with."

Stewards' barrister Albert Dinelli noted only a sub-group of the 17,000 texts were relevant to the case.

Some of the texts and information about the stewards' case were published in a newspaper, prompting a couple of defence lawyers to raise the issue of whether their clients could receive a fair hearing.

Bowman said the leak was disappointing but ultimately did not affect the case.

"Disappointing as it may be, the leaking of the material provides absolutely no grounds for arguing that the prospect of a fair hearing has been compromised or adversely affected."

Bowman said no information was published that everyone involved in the case did not already know and stressed it was not a criminal trial involving a jury.

Bowman criticised the RV stewards over the summary of evidence initially provided to the defendants, describing it as disappointing and effectively useless.

But he rejected requests to postpone the two-week hearing beginning on April 30.

The investigation was sparked by the withdrawal of the Smerdon-trained Lovani from a Flemington race in October because of a suspected race day treatment.

The eight charged all had links to the Aquanita Racing group, Bowman said.