Dyfed-Powys Police said its officers made arrests relating to controlled drugs at the dance party near Llanddewi Brefi over the bank holiday weekend.
Local people and councillors have called for action to ensure more raves are not held.
Organisers of the event had relayed the remote location to people via text and email rather than social media.
Police said they became aware of a "large gathering" late on Saturday, 28 May but because it was already on a  "a very large scale" the decision was made not to break up the party.
Instead, officers stayed at the event to ensure more people could not enter the site.
The police helicopter helped to gather intelligence and evidence and arrests were made.
Llanddewi Brefi councillor Rhodri Evans said: "I have had quite a few people in Llandewi expressing their concerns - people driving through the village at very high speeds and perhaps putting people in danger."
He added that the area was "quiet and peaceful" and villagers wanted to ensure more raves were not held.
Officers have urged landowners to be vigilant to people enquiring about their land in the guise of hiring it for apparently acceptable activities such as gymkhanas and scouts and guides events.

Pro Rugby America, in a statement, described Pro12 as an "interloper" and claimed the league "does not have a legitimate business plan."
Pro12 officials held talks about US and Canadian sides being involved, which had been backed by World Rugby.
"It's ridiculous. What they're doing is just disrespectful," Pro Rugby America chief Doug Shoninger told BBC Wales.
"I understand Pro 12 is under a lot of stress, a lot of problem, but it's not our problem. And they need to solve that problem where they sit."
Pro12 is made up of four teams each from Wales and Ireland plus two each from Scotland and Italy.
Pro Rugby America is sanctioned by governing body USA Rugby to run a professional rugby division in the United States.
The US league started in April with five teams based in Denver, Ohio, Sacramento, San Diego and San Francisco and Shoninger told BBC Radio Wales they were negotiating a deal with the southern hemisphere Super Rugby league.
"We're bidding on a Super Rugby team," he said.
"We're talking to big established countries, ones I feel that have player exchange at academy levels.
"We're very honest about who we are - we have the potential great commercialism and we need the support of the rugby world to build up our infrastructure."
Pro12 is commercially smaller than the English and French professional leagues, and in August, Scottish Rugby chief Mark Dodson said they were "seriously investigating" the possibility of expanding into the American market.
The two Italian teams that compete in the league, Zebre and Treviso, have faced calls to be dropped from the Pro12 and were almost expelled in 2015 over money owed to the rest of the teams.
Pro12 Rugby declined to comment.

Sixteen candidates stood for 16 vacancies on the island's government the Chief Pleas last December, so there was no vote.
Howard Knight, who was commissioned by the Chief Pleas to oversee the election, said it was not a good result for democracy.
The Chief Pleas said his report would be discussed next month.
The Chief Pleas has a total of 28 members or conseillers which govern Sark, one of the smallest of the Channel Islands, with a population of about 600.
Instead of the election, there was a ballot on which candidates would serve for four years and which would serve two.
However, Mr Knight said he found that there was no "conspiracy" and that the unusual situation was a coincidence.

M2 Subsea - headquartered in Westhill - will tackle explosive devices lying at the bottom of the Baltic Sea since World War 2.
Two remotely-operated vehicles (ROVs) will work from the Go Electra support vessel.
The contract was awarded by Next Geosolutions.
M2 Subsea chief executive officer Mike Arnold said: "This contract award from Next Geosolutions is great for the business and a significant scope of work for us to win.
"It highlights both our capabilities to negotiate what is a very challenging subsea environment.
"Safety is a key factor on every project and in particular where it involves surveying the seabed to identify undiscovered explosive devices for removal."
Police are investigating after about 2,000 people turned up for a three-day illegal rave in Ceredigion.
[NEXT_CONCEPT]
Plans for American sides to join the Pro12 have been dismissed by the company running the pro game in the US.
[NEXT_CONCEPT]
Sark needs to improve the health of its democracy, says an election observer after the last election was scrapped.
[NEXT_CONCEPT]
An Aberdeenshire subsea business has won a contract worth more than £1m to remove explosives from around the world's longest pipeline.